I am posting this here because I didn’t get any kind of response in the kits forum:
I just received and assembled the variable load board.
I am able to connect to it with a terminal program and set the voltage and current but when I try to turn on the load the LED blinks but does not stay on.
I presume that the LED is blinking as an acknowledgment of a press of the capacitive switch or receipt of a serial command.
I was trying 5V at 200mA which is well under the 15 Watt maximum.
I measured 10K Ohms between ground and the case (nut & bolt) of the transistor.
Additional symptoms:
Pressing the up capacitive switch does not always raise the current (most of the time it doesn’t)
Even when it does increase the current the LED does not blink
Pressing back resets the load but does not blink the LED
The down arrow does not always decrease the current but it does always blink the LED
All tests were tried with a load (22 Ohm wire wound resistor) and without a load connected.
I connected the load to a power supply with the load and power supply set for 5V and the load set for 1A and the power supply current limit set to 1.5A. And still the LED just blinks when I press the enter capacitive switch or the E1 command.
When I turn on the power supply output I see a V source of 4.97V. The I source is 0.000.
I am able to get the eload to work occasionally by pressing the enter key but more often than not the LED just blinks and nothing else happens. I can turn off the eload with the E0 command but it will not turn on with the E1 command.
Sometimes if I press the enter key the eload resets as if I pressed the back key.
I don’t have an I2C display to connect at this time.
I briefly talked to TS-Russell in the evening about it and tried testing a known good with a [5V/1A power supply that I had around in one of my projects. Setting the current limit to 200mA with the capacitive touch button, it worked as expected.
Care with the Small Capacitive Touch Buttons
I did have to be careful about using the capacitive touch buttons. They were a bit small compared to the size of my fingers and I accidentally triggered the adjacent capacitive touch buttons.
No Load?
I did noticed that when there was not a load connected, it would do some funky things. The LOAD_ON LED would not stay on and the current would reset when pressing the ENTERcapacitive touch button. The current limit would also not adjust when pressing the ^ or v capacitive touch buttons. You might want to check your solder joints for loose connections. You may be able to see the voltage source as 4.97V but perhaps there is something loose or not fully connected causing the settings to reset.
Type of LCD
On a side note, the Variable Load was designed to work with a basic character LCDs through the parallel interface (not I2C LCDs ;D).
Troubleshooting
Hmm. If you can, try posting images of your solder joints for the transistor, heat sink, and screw terminal for the output load as TS-Russell requested for the [Variable Load Kit. This is to see if the solder joints might be causing any issues similar to what I saw when there was no load.
If you can, try also cleaning any flux residue if you were using water soluble flux to solder the components to the board. I wonder if the flux residue is making dendrites and temporary shorts on the Variable Load, thus possibly causing the board to reset? I have seen issues where users attempted to upload code betwen a USB-to-Serial and Arduino, it failed due to the flux residue. I haven’t heard of flux residue specifically causing problems when the board is running but this could be another avenue to check.](https://www.sparkfun.com/products/14449)](https://www.sparkfun.com/products/retired/8269)