JimStim 1.5 V2.0.3 Power Supply Experience
Posted: Mon Feb 16, 2015 12:50 pm
Gear:
JimStim 1.5 w/ 2.0.3 firmware
12VDC 500mA wall wart
BK Precision 1670A power supply
Fluke 87 v.5 multimeter w/ thermocouple
I decided to post this after running into some issues with my Stim build last night, and reading this thread.
After completing the build, I used a 12 volt DC wall wart that came with my Canadian Tire LED trouble light. It's rated as 12VDC, 500mA with the correct plug used by the Stim. I plugged it in, switched on the Stim for the first time and nothing happened at all - no power LED. Disheartened, I flipped the switch to the other "on" position and success, though the light looked a little dim. I ran through the LED and function checks listed at the end of the build instructions and everything checked out fine, but when I started measuring voltages, things started going off the rails (ha!).
When turning it on, I couldn't help notice that the power LED would momentarily light bright, then fade slightly. I started poking around with the meter to see what I could see. The 12V header was reading 4.000, and the 3.3V header was a solid 2.97. Using the thermocouple I checked the temps at D1, D4, F1 and the processor. They were all slightly above ambient - perhaps 1.5'C but nothing of note. I measured power at the X1 terminals - 4.8 volts. It was sure acting like a short, but there was no heat anywhere and while my soldering is best left hidden, a thorough exam under the magnifier showed no solder bridges.
I did a quick google search and came to the thread linked above. Following instructions from JB there, I removed the processor and measured again. Again, low readings:
This morning I ditched the wall wart and dragged out the old BK bench top supply. I set it up for 12VDC, dialled down the current limit lest I set free the smoke monster and switched it on. Things got better immediately! Bright LED! Measure the voltage at X1 - 12 volts! The BK is set with a 40 milliamp current draw limit and with no processor in place it runs fine. I'm skeptical of the number so I checked current draw with with the Fluke. Meter shows just 20 milliamps.
No processor:
So now these numbers look pretty fine LEDs light, Bi-Polar LEDs light both ways, function tests both check out, voltages check out - I dare say we have a winner!
For entertainment, I disconnect the BK and wire in the supplied 9V adapter to run the Stim on a trusty old 9V battery I find laying around.
Being aware of the following helped tremendously:
Oh yeah - and the power switch only works one way.
JimStim 1.5 w/ 2.0.3 firmware
12VDC 500mA wall wart
BK Precision 1670A power supply
Fluke 87 v.5 multimeter w/ thermocouple
I decided to post this after running into some issues with my Stim build last night, and reading this thread.
After completing the build, I used a 12 volt DC wall wart that came with my Canadian Tire LED trouble light. It's rated as 12VDC, 500mA with the correct plug used by the Stim. I plugged it in, switched on the Stim for the first time and nothing happened at all - no power LED. Disheartened, I flipped the switch to the other "on" position and success, though the light looked a little dim. I ran through the LED and function checks listed at the end of the build instructions and everything checked out fine, but when I started measuring voltages, things started going off the rails (ha!).
When turning it on, I couldn't help notice that the power LED would momentarily light bright, then fade slightly. I started poking around with the meter to see what I could see. The 12V header was reading 4.000, and the 3.3V header was a solid 2.97. Using the thermocouple I checked the temps at D1, D4, F1 and the processor. They were all slightly above ambient - perhaps 1.5'C but nothing of note. I measured power at the X1 terminals - 4.8 volts. It was sure acting like a short, but there was no heat anywhere and while my soldering is best left hidden, a thorough exam under the magnifier showed no solder bridges.
I did a quick google search and came to the thread linked above. Following instructions from JB there, I removed the processor and measured again. Again, low readings:
- X1 4.87V
- 12V header 4.054V
- 3.3V header 3.078V
This morning I ditched the wall wart and dragged out the old BK bench top supply. I set it up for 12VDC, dialled down the current limit lest I set free the smoke monster and switched it on. Things got better immediately! Bright LED! Measure the voltage at X1 - 12 volts! The BK is set with a 40 milliamp current draw limit and with no processor in place it runs fine. I'm skeptical of the number so I checked current draw with with the Fluke. Meter shows just 20 milliamps.
No processor:
- X1 12.01V
- 12V header 11.24V
- 3.3V header 3.295
- X1 12.01V
- 12V header 11.24V
- 3.3V header 3.294
So now these numbers look pretty fine LEDs light, Bi-Polar LEDs light both ways, function tests both check out, voltages check out - I dare say we have a winner!
For entertainment, I disconnect the BK and wire in the supplied 9V adapter to run the Stim on a trusty old 9V battery I find laying around.
- Battery w/o load: 9.03V
- Running @ X1 8.75V
- 12V header 7.93V
- 3.3V header 3.290
Being aware of the following helped tremendously:
- The 12V header is not stepped up or regulated 12V, it's whatever is applied at the input less the voltage drop across the diode at D1.
- There is no 5V at the 5V header with no MS connected.
- A plain old 9V battery will run your 3.3 header to 3.3VDC and support all the LED and function tests with ease.
Oh yeah - and the power switch only works one way.