Tom Log

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Contents

Tom Griffing's Log

Tom photo.png

Fri Feb 29, 2020

Back to the Light Dimmer application: Here is a video showing it working from an Arduino Uno:

Light Dimmer Circuit Test


Fri Jan 31, 2020

Light Dimmer board layout:

Board Layout

This is a hand drawing of the traces to copy to the copper-clad circuit board before etching. We found that using a black "Sharpie" marker resulted in ink deposited that did not dissolve in the etching solution (2 parts hydrogen peroxide, 1 part muriatic acid).

About the board layout:

  • The IGBT is the only component to be mounted on the copper side of the board. A hole should be drilled to allow for a mounting screw
  • The cross-hatched area under the IGBT and surrounding the STEAM should be solid copper, to dissipate the heat from the IGBT. This is why it is mounted on the under-side of the board.
  • Elliptical holes are between the board edge and the connections for large wires (AC in and lamp), allowing for zip-ties to provide mechanical support to prevent the wires from moving and ripping the traces from the board (as was our experience).

Fri Jan 31, 2020

Found the Amazon page for the LED driver module for the LED to be used with the battery pack:

LED driver module

It list the module with the following information:

Shouhengda LED Constant Current Driver Power 10W Power Source
by Shouhengda
5.0 out of 5 stars 2 ratings
Note:
This item is only available from third-party sellers (see all offers).
Available from these sellers.

    10w LED driver
    Input Voltage:DC12-24V
    Output Voltage:DC3-12V
    Waterproof Rank:Non-waterproof
    Item included:1pcs Constant Current LED Driver


Working with the Raspberry Pi 4 hardware, making a tablet. Don had trouble with the NOOBS package installation and we drove to the local Dairy Queen for ice cream sundays and to use their WiFi to download the proper package, as we are approaching the limit of data at the farm.

Continued working on the Light Dimmer board layout. Switched to the battery module, adding wiring and set screws to the module and also adding modules for charging and power delivery via a boost converter.

I was testing the battery charging module, charging one battery. I placed an ammeter inline with the module and measured 1.5 Amps. Its lights were blinking and it became too hot to touch. I moved it for a better view and the micro USB connector came free from the module - it must have been hot enough to melt the solder.

Interesting excerpt from the module documentation:

Trickle charge (battery reconditioning) - if the voltage level of the connected battery is less than 2.9V, the module will use a trickle charge current of 130mA until the battery voltage reaches 2.9V, at which point the charge current will be linearly increased to the configured charge current.

This "configuration" is a surface mount resistor on the top side of the module circuit board - and it is not easily changed.

I connected 5 batteries in parallel to the charger, even though it said it could take one or two. After a time, the charging board was cool and the red light lit, meaning it is charging.

Moved on to the LED element for the Raspberry Pi. It has a driver module.

Info for battery protection module:

[1]

Battery Charging Module

Datasheet for boost converter:

XL6009 400KHz 4A Switch Current Step-On Power Converter Module

Amazon Boost Converter [Boost Converter]

Thu Jan 30, 2020

Working with the PWM Light Dimmer board. The part I was using in testing has been replaced with the MJE13003 transistor. They are both NPN transistors, but the pinout on the documentation is confusing, as it appears to order pins from the back of the device:

MJE13003-Pinout.png

MJE13003 Datasheet

To verify, I used a multimeter on the "Diode" setting to verify the direction of the PN junction from Base to Emitter - this measures like a diode in that the current flows from Base to Emitter, but not the reverse.

Conclusion: The pins are ordered according to the front of the device - the side with writing and the diagram appears backwards.

Wed Jan 29, 2020

After breakfast, took another look at the Arduino board and realized that we had not cut some foil traces on the board, causing it to not work. Corrected it and success - it started working.

Conferencing with the other sites, I reviewed the Instructional on PWM Power Control:

| PWM Power Control

After the Instructional, we went to the shop and got into making chargers for the batteries and getting them charged and started work on designing a circuit board for etching to implement the "Light Dimmer". Jessica drew the lines of the circuit board with a sharpie. After etching, excess copper had been dissolved. We assumed it was due to streaks in the sharpie lines, so for the next one, we went over some of the lines with a blue sharpie. Upon etching, we noticed that blue ink had dissolved and copper underneath had dissolved.

Also: My water heater seems to have sprung a leak.

Tue Jan 28, 2020

First day of Arduino electronics course went slowly, due to the introduction to "hands on" electronics and we had 4 Arduinos to build, but only two soldering irons, one of which had a tip that didn't "wet" well.

The USB - Serial converter we were using did not have some of the pins as in the reference materials, specifically the pin that went to the "Reset" pin on the Arduino. This may have been why Don's Arduino was recognized, but would not accept an upload file.

Drove to an auto parts store and bought two soldering irons - 30 and 60 watt irons for the Arduino and the following Power Electronics.

All in all, a good day in the shop - working with Arduino electronic assembly.

Mon Jan 27, 2020

Printed a holder for a pen and the height sensor and used it to replace the extruder and do pen plotting instead.

Sun Jan 26, 2020

Completed the D3D Universal printers and printed some test prints, including a linear bearing for a 1" steel shaft. Test fitted it with a 1" steel shaft.

Sat Jan 25, 2020

Building the D3D Universal printer.

Fri Jan 24, 2020

From the FreeCAD class, designed a screwdriver handle for a hex bit:

File:HexDriver.fcstd

Fri Jan 24, 2020

Worked on the design of the battery charger. This is the schematic at present:

BatteryChargerSchematic.png

Marcin and I will pick up some parts from an electronics store on the way to pick up Don from the airport.

Thu Jan 23, 2020

Made a last minute trip to the farm, bringing a load of things that will help the workshop go more smoothly.

Continued design of battery charger circuit. I think it is largely complete - now the work begins on Arduino software to implement the charging rules:

Picked up Marcin at the airport, took him to a thai restaurant (his favorite).

Tomorrow: Pick up Don and head for the farm.

Thu Jan 16, 2020

Removed blown IGBT, re-soldered another.

I am searching for a larger inductor, as it will be critical for controlling output current to prevent frying another IGBT.

Here is a photo of the ones already fried:

4BlownIGBTs.png

3 of the 4 have pieces blow out from between the collector and emitter (where the high current is flowing). Looking at the tiny leads, I doubt they can handle the current quoted in the specs (Continuous 60A?). I think its worth doubling up on IGBTs to improve the current-carrying capacity of the circuit.

Began Welder BOM:

[2]

Question:

 * Will OSE supply / print the electrode holder? If printed, where will metal parts come from?

Spent time re-thinking the circuit, studied it closer and found some signals driving the transistors that I didn't like. Re-designed the circuit to not invert the signal and built a new prototype using two IGBTs in parallel this time. Connected it to power. It survived at 30% duty cycle - it produced some sparks at the electrode and made the tip of the rod glow red. Increased to 60% and it did much the same. But when I increased to 100%, POP went both IGBTs.

I have some more ideas I can try tomorrow.

Wed Jan 15, 2020

Attended the weekly meeting, talked with Michel for a time, but had to leave after ~30 minutes.

Drove to farm, connected the new circuit to the batteries, tested at low-PWM: nothing, tested at max-PWM and "POP" went the IGBT - again.

Tue Jan 14, 2020

I've reached the end of low power testing and it's time to scale up. Re-soldered the connections to the output components and packed for testing at the farm tomorrow.

Mon Jan 13, 2020

OK ... got done with work, now back to the welding circuit. I wasn't comfortable with the calculation for the inductor value below and somebody corrected it (thanks again). I did a search for "L C filter Calculator" and found a site: Low Pass Filter Calculator In the section "cutoff frequency at LC low pass", I plugged in the values for my components:

2.29 uH inductor 47uF capacitor

It gave the answer: 15.34 kHz

While this seems like a fine answer, it doesn't mesh with my testing, as it didn't pass the pulses at low frequencies and most of the output voltage was found to be across the inductor and not on the load. Weird how things in the "real world" don't work as expected. I'd like to think this was due to the rectangular pulses, but it also occurred at 100% duty cycle (basically DC). Ugh - finally found out what was going on ... the coil I am using is actually two coils and wasn't passing the current. OK ... it makes sense now. This coil has PCB mounting and the actual wiring of the coil is difficult to see.

This split coil presents two options for the circuit:

  • Connect the coils in series for the full 2.49 uH
  • Connect them in parallel (careful with directions of windings) for half the inductance, but double the current capability.

Also: I was expecting one coil, rather than a split coil. I corrected the wiring by removing the capacitor and re-connecting the inductor and now power is getting to the load.

I had disconnected the capacitor and think I'll leave it that way, as the coil is more important for limiting fast changes in current. Next: How fast do we run to make the most of the inductor when connected to a low resistance (ie: a welding rod)? I will assume the resistance is around 1 ohm for the wiring, connectors and welding rod.

Let's find the optimal frequency using the "R L Low Pass" Calculator from the website above. For 1 ohm and 2.29 uH, it yields 69.5 kHz. That's interesting, as it is twice the frequency I've been able to get out of the Arduino. I don't see how to double the frequency to 62.88 kHz. If anybody can find the code, send it to me. Meanwhile, let's proceed using 31.4 kHz for the base PWM frequency.

Sun Jan 12, 2020

Found the line in Arduino code to hike the frequency to 31.4 kHz:

int PWMPin = 6;
int potPin = 0;
 
void setup() {
  
  TCCR4B = (TCCR4B & 0xF8) | 0x01 ; // Set frequency on Timer4 to 31.4 kHz
  pinMode(PWMPin, OUTPUT);
  pinMode(potPin, INPUT);
  Serial.begin(9600);
 
}
 
void loop() {
  
  int potValue = analogRead(potPin);
  analogWrite(PWMPin, potValue/4);
  Serial.println(potValue/4);
 
}


Question: Will this code work on the Arduino being supplied in the workshop?


Now to test the welder at the higher frequency and with inductor and capacitor ...

Sat Jan 11, 2020

For the AC welder, we would best use a transformer for the welder output for several reasons:

  • Reduce the current switched by the transistor(s)
  • Increase the current while lowering voltage to the output
  • Use inductance in handling the power, as it will smooth fluctuations

That being said, let's return to the DC welder. In my prior attempts, it has demanded more current than the IGBT can handle and resulted in crispy IGBTs. We can continue, but add an inductor inline with the output to limit current spikes and smooth out the power to the welding. Something like this:

Buck-24V-welder.png

I've thrown in some values for the inductor & capacitor and have not changed the frequency of the Arduino PWM output. The reactive components (inductor & capacitor) are frequency sensitive and will be more effective at higher frequencies, but we don't want to go too high, as it will increase heating in the IGBT.

I'd like to know the inductance of the coils I found, but I don't have a meter that measures inductance.

I checked the web and found a page with formulas that can calculate inductance of a torid coil from it's geometry:

Calculate Inductor Value

After finding the correct formula (torid core 3.5" OD with ferrite rectangluar core), it yielded the following:

Inductance in uH = 0.002 × 26² × 2 × ln( 3.5 ÷ 1.5 ) = 2.29 uH

Note: Somebody corrected my calculation (Thank you!). I got the answer from the "calculator" application in Linux Mint, but it yielded the wrong answer. I assume it didn't understand the "ln()" function:

Calculator-ln-error.png

Anyway, on with the implementation. I updated my test circuit with the choke and capacitor I had on-hand and will test in the morning if they can prevent frying any more IGBTs.

I still have not updated the code in the Arduino to adjust the frequency higher. That will be next ...

Fri Jan 10, 2020

Began early, checked on design proposed in article below (Jan 8), but it is beyond the scope of this workshop. Now, to find something simpler.

Here's an early schematic for using 120VAC for the welder:

Buck-120VAC-Welder.png

While this circuit would deliver power output with lower voltage, I doubt it could deliver the current necessary for welding. After all, it is still limited by a 15 Amp circuit breaker, while the welding needs a minimum of 20 amps for the smallest of rods (1/16").

Thu Jan 9, 2020

More cleaning / reorganization of workshop. Bought light fixtures for workshop.

Wed Jan 8, 2020

I did read about buck converters a while back and thought they could apply to the OSE welder.

I ran across one statement that I wish I had seen a month ago, describing the benefit of inductance in welders:

“Short circuiting an electrode with such a [CV, MIG] power source would drop the arc length and the voltage to zero. This, in turn, would cause the current to rise to very high values very rapidly, with the result of causing the electrode to heat by Joule heating with great rapidity and explosive force, causing severe spatter and, possibly, lengths of unmelted wire stuck in the weld pool. To prevent this from occurring, impedance is built into such power supplies to limit the rate of current change, thereby reducing the likelihood of electrode overheating and explosion, and allowing short-circuiting transfer to take place.”

- excerpt from https://corescholar.libraries.wright.edu/cgi/viewcontent.cgi?article=2172&context=etd_all

The article in the link also discusses a portable welder similar to the Fronius, but powered by 2 car batteries and using a "buck switcher". Their design uses 4 power MOSFETs in parallel, as it has low power dissipation while switching 25V - 27V from batteries. Adding an inductor can serve to limit the current without the need for feedback. If in a buck converter, it will give better voltage control.

More reading to do . . .

Sun Jan 5, 2020

Assembled the circuit for testing the welding application.

First, used two 12V, 7.5 AH gel cell batteries connected in series - they didn't produce enough power for welding.

Switched to larger 12V lead-acid batteries - one free standing, the other the battery in the tractor - connected via jumper cables. During testing, burned through 1" of a 1/16" electrode, but blew 3 IGBTs due to excess current - see video below.

Welding Blown IGBT

This one was at approx 20% duty cycle:

Scope-20-duty-cycle.jpg

We will have to do something to limit current through the IGBT. The PWM was operating at 490 hz and the testing was performed with different duty cycles from 15% to 100%. This video shows a stronger arc before the IGBT fried - this was at 100% duty cycle:

Welding Blown IGBT 100%

Note that these were the FGA180N33ATD IGBTs, which are rated at 180 Amps, but when the electrode is touched to strike an arc, it is essentially a short circuit, causing an over-current situation which destroys the IGBT.

How to limit the current?

  • Implement current feedback to modify the PWM duty cycle
  • Increase the frequency
  • Add an inductor in series with the load to limit the current

Sat Jan 4, 2020

Mounted IGBT on heat sync, used second hole in heat sync to attach large wires and improvised a strain relief bracket, then soldered wires to IGBT leads. See photo.

IGBT and wires Mounted to heat sync

Went to Harbor Freight for 1/16" welding rods - they were on sale for $6.99 / lb. Also got an electrode holder and ground clamp for testing.

Fri Jan 3, 2020

Responded to Marcin's inquiry about IGBT package:


Marcin;

The one I'm testing is the FGA180N33ATD, which has a TO-3P package, which is comparable to the TO-247.

The only issue with it is the max voltage is 330V and I'd prefer some headroom, so I specified the FGH60N60SMD, which has a max voltage of 600V and a TO-247 case.

I have attached datasheets for both and the illustration below shows the package similarities.

Package compared image datasheet for FGH60N60SMD FGA180N33ATD

Tom


On 1/3/20 9:24 PM, Marcin Jakubowski wrote: > Tom - is this the transistor you're testing? > > https://www.ebay.com/itm/10Pcs-Lot-Fgh60N60Smd-Fgh60N60-600V-60A-Field-Stop-Igbt-To-3p-RS/113661505571?hash=item1a76c0f023:g:zMAAAOSw1ZBbk2uw > > Did you ever order any next size up TO-247?

Thu Jan 2, 2020

Found a suitable IGBT, added to the Power Panel Parts List.

Will prototype with components on-hand using a circuit as in the following document:

https://docs.google.com/presentation/d/1GoTLn8hJshWwvKa5vzxQ5rbOeKhTnvcSytF6w1g60Ww/edit#slide=id.g5c3be0ce2d_1_28


Thu Jan 2, 2020

Wed Jan 1, 2020

Arduino Power Electronics Tutorial.

I have an update on the instructional.

The light dimmer circuit will look like this:

Light Dimmer Circuit.png

Did some testing with the 120V circuit and it worked as expected for dimming the light bulb. Note: The IGBT I am using (30F124) is getting hot as it is dissipating power for switching the light bulb.

Sun Dec 29, 2019

Power Elecronics Working Doc. Continued reorganizing. Also updated the parts information on the power board. Did some checking on specifications on circuit breakers, found some interesting information on trip times:

File:Circuit-breaker-trip-times.jpg

Fri Dec 28, 2019

Spent half the day reorganizing the house/workshop.

Online meeting with Marcin and Michele (Belgium). One part of the discussion was to filter the input power for the light dimmer and a capacitor was suggested. Some searching turned up this one: 470uf, 400v capacitor

Fri Dec 27, 2019

Continued work on Arduino PWM Instructable. Power Panel Part List.

Wed Dec 25, 2019

Updated the circuit to use an NPN transistor and an IGBT.

I used an LED and resistor for the load and this can be changed for a higher power load, but we'll have to add a heat sync to the IGBT.

Since IGBTs usually require at least +15 Volts from Gate to Emitter (Vge), I added an extra 18V power supply as shown.

The Arduino only outputs +5VDC and doesn't have enough voltage swing to drive the IGBT, so I added an extra "pull down" transistor to pull down the 18VDC to nearly 0.

Necessary resistors also added.

Re-calculate the resister in series with the LED for the change in voltage:


Original LED current for 5V supply and 220 ohm resistor:

  • 5V - 1.2V = 3.8V
  • The LED current is = 3.8V / 220 ohms or 0.0172727 Amps


New Resistor value for same current with 18V supply:

  • 18V - 1.2V = 16.8V
  • The new resistance for the same current is = 16.8V/0.0172727 ma or 972.63 ohms. For simplicity, we can use a 1kohm resistor.


Here is the schematic:

Arduino-PWM-IGBT-LED.png


And here is the working setup:

Arduino-PWM-IGBT.jpg

Tue Dec 24, 2019

Arduino PWM testing.

  • First: Use Arduino to drive LED with adjustable PWM duty cycle. This photo shows about 75% duty cycle.

This is the schematic:

Arduino-PWM-LED.png

And then the testing:

ArduinoPWM-LED.jpg

I found a website for searching transistors: AllTransistors.com

I did some searching and found one IGBT with TO-3PN package, high current capability and low saturation voltage (Vce): FGA180N33ATD. They are available on eBay for a little more than $3 each from a US source:

eBay link IGBT

After some more comparing, I placed an order for 8 of them.

Now, back to PWM testing ... Adding an IGBT to the mix. Checking the spec sheets, we'll need 15VDC to the gate of the IGBT just to turn it on.

Sun Dec 22, 2019

Continued cleaning the house and reorganizing the workshop. A room in the back of the workshop has enough table space for 2 or 3 people to use for the project. It also has a wood-burning stove.

Visited with neighbors, who have some electric heaters and cots we can borrow for the workshop.

Sat Dec 21, 2019

The workshop needs a lot of attention, in order to prepare for the OSE event. moved equipment from inside to the back - under cover.

Fri Dec 20, 2019

Continued writing instructional, cleaning and reorganizing.

Thu Dec 19, 2019

Started writing instructional material for the course on electronics and PWM control for 3 applications:

PWM Course


Wed Dec 18, 2019

Here is a tutorial on using the Arduino as a "light dimmer", to dim an LED:

Arduino light dimmer

We can do this at first, then use the output to drive an IGBT to dim a more powerful light.

Tue Dec 17, 2019

Received the IGBTs today - they are pretty small and don't appear to have much surface area for the heat sync. Since I received 6 of them, I can stack some for testing. I'll probably have to find something more substantial.

Upon looking at the following web page about the Arduino Uno, the frequency can be set and a loop run with each cycle turning on and off the output for a fraction of the period to produce a pulse. This takes more of the processing time:

Arduino Uno PWM

The Arduino Mega has PWM circuits that once started, only need updating if the pulse width changes. This allows the processor to do other things between updates - like monitoring output voltage and current in order to adjust the pulse width for "hot start" and "voltage cutoff".

Fri Dec 13, 2019

I pulled up a video reviewing a cheap Chinese IGBT welder and they use the FGH40N6S2 IGBT - but in their design, they use it to switch high voltage/low current, whereas we will need low voltage/high current, with no transformer. The caveat of this design is the increased power dissipation in the IGBT, compared to the MOSFET.

How does one select an IGBT? I'm leaning toward one that is for sale at a reasonable price, that fits the minimum requirements for switching ~50VDC at 100A at about 20 kHz. First, I go to eBay and enter "IGBT", then start scrolling. I came across a GT30J124 that looked good (600VCES and 200A Pulsed), then entered "GT30J124" into a search engine, where I found the data sheet:

GT30J124 Data Sheet

Strange: The data sheet lists it as both an IGBT *and* a MOSFET.

It appears to meet my specs and is available on eBay at 6 pieces for $10.00, free shipping from Miami - so I ordered some.

Note: this one says 30A, not 100A. See [3] - MJ

Thu Dec 12, 2019

Welder switching semiconductor: IGBT or MOSFET? This page discusses the differences:

IGBT or MOSFET: Choose Wisely

The welder application falls somewhere inbetween two devices - either would be suitable, but I'll need to check specs of specific devices.

Candidates:

Make Part # Type Voltage Pulsed Current On Voltage On time Off time
GT30J127 Toshiba IGBT 600V 200A 1.59 25 ns 182 ns
IRFP3206PBF International Rectifier MOSFET 60V 200A ???? 100 ns 70 ns


The max voltage (source to drain) of the MOSFET is only 60V and I don't think this is enough margin for the welder output voltage - especially for the case for longer arcs, which cause the voltage to rise. I saw one reference, saying it could go up to 100V. Higher voltage MOSFETs are available, but at lower currents. This leads me to IGBTs.


Arduino:

The ATmega168P/328P chip has three PWM timers (Timer 0, Timer 1, and Timer 2), controlling 6 PWM outputs. The two outputs for each timer will normally have the same frequency, but can have different duty cycles.

This document describes the details of the PWM controls.

For the welder design, I suggest using "Fast PWM Mode" (WGM set to 011) as below on pins PD5 and PD6, but adjusted for about 20khz:

pinMode(3, OUTPUT);
  pinMode(11, OUTPUT);
  TCCR0A = _BV(COM2A0) | _BV(COM2B1) | _BV(WGM21) | _BV(WGM20);
  TCCR0B = _BV(WGM22) | _BV(CS22);
  OCR0A = 180;
  OCR0B = 50;

This uses time 0. I'll have to consult the data sheet for values of "CS" for prescalar values to adjust the clock.

The duty cycles for outputs on pins PD5 and PD6 are set by values in OCR0A and OCR0B.

The PWM output duty cycle will be as illustrated:

Pwm-explain.jpg

Tue Dec 10, 2019

This Video shows welding using only 3: 12V car batteries. That means welding works with 36VDC from lead acid batteries. The test setup worked with 3/32" rods, but not with larger rods. The reviewers said it "welded too hot" with lots of undercut. My take on this is that the batteries' output is not adjusted. A higher voltage would help the arc get started, but the weld will be best if the current is regulated.

Interesting statement I ran across:

"There are a number of devices that probably would not exist without the IGBT (switched high voltage, high current appliances), but a 12V DC motor doesn't really fall into the IGBT required/desired category. For your application, you may be better off with a MOSFET provided you switch it properly."

After thinking about it, "the usual" design of an IGBT welder is to switch the high voltage to drive a transformer, which converts it to a lower voltage with higher current. Since we are designing a welder to would switch low voltage from the batteries (less than 36V), we should instead use a power MOSFET to reduce the power loss.

Some terms:

  • "Anti Sticking" eases removal of the electrode by increasing current to melt the puddle
  • "Hot start" adds current for easy starting of the arc - especially with electrodes that are difficult to start
  • "Arc force" (similar to "arc control" and "dig") increases current as the arc voltage drops (around 19V) - The current doesn't vary much unless the arc is very short
  • "Chopper system" - a low-voltage/high-amperage (85 volts/115 amps) output from the alternator is rectified, filtered with capacitors and then chopped with an IGBT at around 20 kHz. This will increase IGBT heating, as it spends more time switching.

Mon Dec 9, 2019

Spoke with Marcin about January workshop in Texas. I have a lot of preparations to do.

Workshop goals will have 3 components:

  1. Light Dimmer
  2. Battery Charger
  3. Cordless welder

Notes on 18650 batteries:

  • General: Don't discharge to less than 3.2 volts. If voltage not between 3.0 and 4.2V, bad battery.?.
  • Charging: Charge to 4.2 volts MAX (undercharge to 3.8 - 4.0 volts to extend battery life), 300 to 500mA. Never charge when below freezing.
  • Life cycle: Measured when capacity goes to 80% - typically 300 - 500 cycles, 200 for high-amp or high-drain cycles. Many can reach more than 1000 cycles in the right conditions. Good info: 18650 Batteries
  • Thermal: Best capacity at 30 - 60 C, 30% less at 0 C, 60% less at -10 C.

Notes on cordless welder:

It will be powered from a 24 VDC pack of 18650 batteries. Target: Weld with 3/32" rods at 100A. If welding voltage is 20V, this will be 2000 Watts. Welding for 10 minutes would require 10 packs of 6 18650 cells, with cells in a pack connected in series and packs connected in parallel. The electronics will consist of an arduino with shield, arduino power supply, IGBT transistors and an L-C filter for the output.

November 18, 2019

I have reviewed some welder circuits and watched some videos about welders and the designs use high voltage / low amps for the switching & control, then use a transformer to convert it into low voltage / high current for the output for the welding arc. They also include a power supply for the control electronics and multiple circuits for feedback control of the switching.

They also include filters to suppress the high frequencies to reduce the resulting EMI emissions.

Per discussion with Marcin, here is a link to a video we discussed about an evaluation of a 200A IGBT inverter welder:

200A IGBT Inverter Welder

Another video discussing welding transformers:

Welding Transformers

November 12, 2019

OK: Time to get started again. This time, analyzing requirements for the Universal Power Supply.

Stated requirements:

  1. Light Dimmer
  2. Welder
  3. Cordless Welder
  4. 18650 Battery Charger
  5. Motor Power Supply

These are all related to power delivery, but the applications vary widely and the requirements list design specifics that might best be updated.

Since some of the stated requirements are so simple, yet different from others, I will consider them separately.

1. Light Dimmer: The requirement call for a rectifier and a PWM circuit to deliver pulsed DC to an incandescent bulb, whereas typical light dimmers use the combination of a diac and a triac. The triac design is far simpler. I found a very simple circuit that would be easy to replicate:

Screen Shot 2019-11-12 at 6.15.04 AM.png


Source: https://www.electroschematics.com/220v-light-dimmer-switch/

It appears that the goal is not to dim lights, but rather to make a PWM power supply for further use. With that in mind, I'll start searching for welder designs.

2. Welder: While the spec calls for input of 120VAC @ 20A, this would require a special receptacle and plug, as well as a 20A circuit breaker. Most household receptacles for 120VAC are only capable of 15A max. Here is an image of a 20A receptacle:

White-leviton-electrical-outlets-receptacles-m02-cbr20-wmp-64 400 compressed.jpg

Source: https://www.homedepot.com/p/Leviton-20-Amp-Commercial-Grade-Duplex-Outlet-White-10-Pack-M02-CBR20-WMP/203996698

The intent is most probably for generic household electricity, so we should scale back the power to 120V x 15A = 1800 Watts (or: 1.8 kw)

I found a design for a welder using IGBTs, however it is for 230VAC supply, with text in czeck - but it is a good place to start: [4]

Welder-igbt-schematic.png Welder-igbt-schematic-voltage-feedback.png

Another good source for circuit designs is from the manufacturers, as they try to make it easy for their products to be used.

This is a page from Fuji Electric, with designs for welders using their IGBT modules:

Fuji IGBT Modules for Welding machine

I have a HUGE preference for using IGBT modules over discrete parts, as connections are more robust, larger heat sync mounts and simpler assembly. Also: multiple components are in packaged in one housing and they are optimized for one function, like choppers and H-bridges.


3. Cordless Welder

4. 18650 Battery Charger

5. Motor Power Supply

October 9, 2017

Solar_Power_Cube_v17.10

I've been thinking about how to mount the motor to the hydraulic power unit:

 Solar Power Cube Front.png Solar Power Cube - Front View

As shown, the offset motor / gear assembly is awkward to mount and will extend beyond the Power Cube frame (one frame member removed for clarity).

I designed a bracket assembly, but have resigned to re-using the bolt holes in the motor's gear assembly for mounting to the plate on top of the power unit:

 36V Motor Front.png 36V Motor - Front View

The bolts must:

* Provide motor support
* Prevent the motor from tilting with increased belt tension / torque
* Allow the motor to slide from side to side to adjust belt tension

October 8, 2017

Preparing for the Solar Power Cube ... Solar Power Cube Working Document

I have to get everything designed in time to order parts for the workshop. The question has now come up for the pulleys and timing belt and how to attach them to the shafts of the motor and pump. The pump side is easy - 1/2" and positioned higher than the motor. Attaching the pulley for the motor is another question, though the motor is somewhat lower than the pump shaft and the motor shaft is threaded on the end.

The initial question is: Do we make the pulley to screw onto the threaded shaft or slide over the lower part of the 20mm shaft (or both)?

The followup question is: Is a lathe (and someone to run it) available in the OSE workshop in good working order for machining and/or threading the pulley to match the shaft?

Also: How do we purchase the pulley material - in discrete pulleys or in "bar" material?

 5mm pulleys.png 5mm Pitch Pulleys
 Polytech 5mm Pulleys
 5mm bar material.png Pulley Bar Material
 Polytech 5mm pitch bar

Note that the motor pulley will have to be longer than the pump pulley for the belt:

 Belt Pulley Orientation.png Belt and pulley orientation


The length of the shaft shown is short and won't extend through the length of the pulley, so we will have to improvise a solution.

The main "gotcha" is that the full specs of the shaft aren't given - like the shaft length and the threads on the end of the shaft.

OK ... I finally found a closeup of the shaft:

 Motor gearbox.png Motor Gearbox and shaft

April 22, 2017

Checking out the OSE Wiki pages to see if they are read-write . . .

March 20, 2016

Packing the 3D printer for the return trip. Visit with Alec to see the updates on the Micro House 3 and discuss possibilities for utilizing its solar panels.

March 19, 2016

Workshop began - lots of unloading and preparing supplies for the workshop. Built a printer along with the other participants, but had to leave before testing. One local participant offered the use of a facility nearby, so we packed up and drove there. Successfully tested all printers with only one "smoker", which was repaired for total success. Ended at 12:30 AM and drove back to Factor e Farm.

March 18, 2016

Arrived at OSE, checked out the amazing bok choy growth in the greenhouse and the two new puppies. Helped prepare for the 3D printer workshop. Testing the Porteus software distribution with the 3D printer. Cut aluminum plates for the printers. Packed workshop supplies for the morning trip to the workshop location in Kansas City.

March 14, 2016

OK ... there's been a gap in my log. Concerning the upcoming lab for the 3D printer, the original ISO file for the Linux distro wasn't bootable from a memory stick. The site shows how to convert an ISO file into a "hybrid" file, bootable from optical or memory stick:

Here is the original ISO image that didn't work well for booting from USB sticks:

D3D Live ISO

Here is the image for the 3D printer workshop that has already been converted:

D3D Hybrid Live ISO

All that needs to be done is do a raw copy of this file to the USB stick using "dd" (Linux), "Disk Utility" (Mac) or some similar disk utility.

Update: The "ddrescue" program is for data recovery and it addresses a different function.

The "dd" command (ie: "Data Dumper") that I mentioned writes data from an input (ie: ISO file) to an output (ie: the USB stick).

First: Identify the device for the USB stick. You can use commands like "lsblk", the "fdisk -l" or the Ubuntu "disks" GUI to find the device. In a single disk system, the "/dev/hda" device is your main hard drive and "/dev/hdb" is often the USB stick. The following writes the ISO to the "sdxx" device:

dd if=Porteus-D3D-Workshop-x86_64-v2.iso of=/dev/sdxx bs=1024b

Please note that the "dd" command performs a raw write and will overwrite the destination device (ie: "of=..."), including all partitioning, formatting, data, etc.

Marcin Notes

sudo apt-get install gddrescue - installs ISO creation program ddrescue

July 26, 2015

Worked on OSE wiki, fixed an issue with the user account approval.

July 25, 2015

I've been working on multiple fixes and updates for the Power Cube design and recently changed it to version 15.7 in the 3D Warehouse. The changes were adjustments from the results of the July Power Cube workshop.

July 15, 2015

Gasifier Workshiop, Day 2 Torched some steel for the gasifier folk. Didn't get much done as there was a personnel issue. Spent time resolving it and documenting jigs. Marcin bought 5 T Shirts and we discussed further sales - I told him that I could ship them individually.

July 15, 2015

MicroTrac Workshiop, Day 1 Focused mostly on finishing the Power Cubes and with the updates to one engine to enable operation with the gasifier.

July 15, 2015

MicroTrac 2.0 Workshiop, Day 3 Worked on Power Cubes and assisted from time to time with the MicroTrac. Welded the plates in the hole punch to prevent drift. The MicroTrac T Shirts arrived - Sold several.

July 14, 2015

MicroTrac 2.0 Workshiop, Day 2 24 links completed! Discussed the idea of a fab shop in a shipping container.

July 13, 2015

MicroTrac 2.0 Workshiop, Day 1: Late start, as Marcin had an eye issue. Worked with Will Turner to make a jig for cutting and punching chain links. Problem with hole punch - dies getting out of alignment. Made first batch of tracks and tested.

July 12, 2015

PC 15.6 Workshop, Day 3: Met with Marcin and Jonathan for planning, then went to the workshop where everyone was gathered and working. Integration day - we found some design issues along the way:

  • The 4 x 4 tube at the rear of the engine had to be removed before the engine / muffler could be seated.
  • The geometry of the return plumbing could not be used intact and the oil filter had to be unscrewed from the bracket.
  • The keyswitch on the old control bracket conflicted with the 4 x 4 tube and had to be rotated 90 degrees.
  • The 1 1/2" coupling was made of cast iron and posed a problem for welding the Hydraulic Reservoirs.
  • The wiring harness diagram had two wires crossed, which burned out the diodes before the magnetos.
  • The bolts securing the bottom of the oil cooler expanded steel to the lower tube could not fit through to the back side of the tube, as the Hydraulic Reservoir was there - so it would have to be secured with short bolts from within the tube (difficult).

These issues were overcome and four of us (Jonathan, Natalia, Will and I) worked on one Power Cube and finally got it going.

July 11, 2015

PC 15.6 Workshop, Day 2: Met with Marcin and Jonathan for planning, then went to the HabLab for discussion before continuing. Continued welding tanks and started on assembling the modules - oil cooler, return plumbing, pressure plumbing, After burning out the diodes, found some replacements in the HabLab, replaced them and got the Power Cube working around midnight.

July 10, 2013

PC 15.6 Workshop, Day 1: Met with Marcin and Jonathan for planning, then went to the HabLab for introductions and lecture. Spent the time cleaning up the shop in preparation for the workshop. Proceeded afterward to the workshop, held the safety briefing and started the build. We planned to do the "dirty stuff" today, cutting steel & welding. The tanks took the full 3 days to complete. Moved the LifeTrac near the door, ran the hoses between it and the iron worker and cut steel for the tank end plates. Only one MIG welder worked initially. Marcin told me what had to be done and I disassembled, replaced liner and wire on two other welders to get them working.

July 9, 2013

Continued cleaning the shop and organizing for the workshop.

July 8, 2013

Arrived at KCI. Marcin arrived in the truck and we drove to MoKan Fasterners for bolts, Harbor Freight for tools and then for Factor E Farm. Spent several hours resolving automotive issues. Spent time organizing the shop and layout out supplies.

June 19, 2015

Updated MediaWiki with extension to require admin approval for new accounts. The other means of blocking spambots just wasn't working. Uploaded newest Power Cube 15.6 BOM.

June 1, 2015

Updated MediaWiki to enable ReCaptcha. Still having some issues with bogus user registration.

January 17, 2015

Power cube arrived this week (Yahoo!). After the shipment, the shipping company charged me an additional $84.60 for a "limited access fee". They claimed the fee is standard across the shipping industry when delivering to schools/universities.

January 13, 2015

Power cube shipment delayed to avoid holiday shipping maddness. Shipped Power Cube kit (ie: Power Cube, less engine & battery).

October 26, 2014

Received an order for a Power Cube, Version 7, less the engine. I've been updating the Sketchup model to include the pressure relief valve and the updated BOM for current pricing. Now to complete the model & BOM and start ordering parts tomorrow. I've also begun inquiries about information about sensors for the hydraulic flow, pressure and temperature - to accommodate new power cube certification requirements.

MicroHouse 4 Workshop

Attended this workshop to get better acquainted with MicroHouse design and CEB construction techniques.

Tue Sep 30, 2014

Back to Dallas.

Mon Sep 29, 2014

Met the electrician from the power company with connectors and tools. Replaced connectors and added MicroHouse wiring. Installed electrical conduit, elbows and ran wiring from the electric panel to the MicroHouse for all lights, sockets, stove and dryer. Other crews completed the roof and began installing windows.

Sun Sep 28, 2014

Painted initial coat on the plywood side of lower roof modules to save time later. Upper roof module construction using screws, 2" x 6" x 16' boards and struts. Other crews installed the roof modules. Dug trench and set conduit into ground for incoming and outgoing cables. Connected the incoming cables to the box main power and prepared connections for the cables to the MicroHouse 3. Secured the electrical connections on the MicroHouse, as it is to "go live" in the morning.

Sat Sep 27, 2014

Lower roof module construction using screws, 3/8" plywood, 2" x 6" x 16' boards and struts.

Fri Sep 26, 2014

Completed digging the trench for the electric cable. Met the electrician from the power company, who opened up the panel only to find that we would need replacement connectors to continue. Closed the panel and informed Marcin of the situation. Worked with several teams to set the CEB blocks for the walls and to make additional blocks from soil and lime. Walls mostly completed today.

Thu Sep 25, 2014

Worked on Micro House misc tasks - including preparing landings and placing the hydronic stove. Checked out the electric panel at the MicroHouse and prepared it to "go live". Drove to Menard's to get supplies for wiring the electric cables from the Micro House to the panel on the workshop.

Wed Sep 24, 2014

Caught a ride to OSE, Missouri with Marshall (from Austin). Checked out the progress made on the Structural Frame Power Cubes and gave a few suggestions for completing one kit.

Sat Sep 14, 2013: 50 HP Power Cube Design

We've had a lot of discussion about the new PowerCube and the new LifeTrac designs and I think I have wrapped my mind around the new frame design. Here is a screenshot:

LifeTrac 35.png

Latest 50 hp Power Cube Suggestion: File:PowerCube 35 Tom.zip

Thursday, July 8, 2013

Drove up to Missouri and to Factor E Farm for the Power Cube / LifeTrac build for Blair Grocery in New Orleans. Spent time designing the new Power Cube with the Kubota diesel engine. Drove to secure the engine, radiator and other parts necessary for the build. Used Sketchup to update the design according to the newly secured Kubota engine. Cut steel for the new 36" frame and began gathering other necessary parts - such as the fan and oil cooler.

James Slade arrived and received instructions to assist with Power Cube development. The crew from Blair Grocery arrived and were oriented for assisting in the build of the LifeTrac. The LifeTrac and Power Cube development proceeded at the same time.

I headed back to Dallas and a few days later, the LifeTrac was functioning and was loaded onto the trailer for transport to New Orleans with the 27 hp Power Cube and the unfinished Kubota Power Cube. The transport stopped at my farm in East Texas, where the Kubota Power Cube was completed, loaded in the LifeTrac, tested and then loaded for shipping to New Orleans - where it was tested successfully.

PowerCube Kubota.png

Latest Kubota Power Cube Design: File:PowerCube Kubota.zip

Thursday, May 25 2013 (Date needs verification)

It's been some time since my last update. The latest activity concerns the new Power Cube design - using a Volkswagen engine. I expect to meet with Jay early this next week to complete the rebuild of the engine and secure the engine. I still have a few more parts to get - especially for mounting the shaft coupling and engine mounts. I have been working on the component layout for the new Power Cube - it will be quite different from before, as the engine/pump mounting is horizontal rather than vertical. Also, the plumbing and engine are larger and heavier and I will be adding a pressure relief valve. The sizing of the hydraulic pump has been a big issue and is documented here:

http://opensourceecology.org/wiki/Hydraulic_Hose_Sizing

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