I'm an electrical engineering student at TAMU working on a project for my first internship: a signal recorder for an experimental helicopter. For context, here are some of my requirements:
- 19 DC analog inputs ranging from 0V to 6V (but could be as high as 24V)
- Must be powered by 24V supply (5V=Teensy, 5V=TLC1543, +/-24V = LM324)
- Must NOT effect the input signal in a noticeable way
To do this, I've designed an Op-Amp Buffer using LM324s and a voltage divider to bring the (potentially) 24V signal into the 5V range. I'm also using a PDM1-S24-D24-S and a SPU01N-05 to try to power the +/-24V for the Op-Amps and the 5V for the Teensy and ADCs, respectfully.
Unfortunately, my design has a major problem: The +/-24V DC-DC converter explodes after a few moments connected to power.
I think it is because the capacitors within the PDM1-S24-D24-S cannot discharge and eventually explode. When I check the resistance between the positive and negative 24V output pins on my circuit, my multi-meter oscillates between a small value (~500 ohms) and an "open loop" message - suggesting that either the resistance is massive or that there is no connection at all.
Above is a rough schematic of what I've currently designed, for brevity I've omitted the other 17 Op-Amps but the pattern of connection continues.
It seems to me that the loads are in parallel, and therefore should have a smaller value (potentially too small, i.e. a short), but my measurements suggest otherwise. I tried adding the 10k resistors to solve this, but the results were the same. Can someone help me identify the problem causing my DC/DC converter to explode? And suggest a solution?
I recognize there are other problems with my design at the moment, but I will ask for help with those on a separate question. But I will happily hear any suggestions that aren't related to the question.
An additional question: Is it bad practice to use a different DC-DC converter to supply the ADCs that will read the signals here? Could it also cause problems with the +/-24V DC-DC?