Hardware design issue

Author	Message
Malibu Senior Member Joined: 07/07/2018 Location: Australia Posts: 261	Posted: 06:16am 04 Dec 2024       G'day all, I've just got my first order from JLCPCB (great service, top-notch assembly; I'm very impressed!) for my 6-channel GP Controller. A simple idea- Webmite controls 6 outputs, depending on the time settings sent through a web browser. After checking all the relevent volts from the (2x) USB connection and the rectified AC supply, I soldered in the Webmite to do some further tests. All good until I fired up the AC supply and found that the 7805 reg is getting pretty hot, plus no output is actually changing state on the ULN output. The input is changing state as expected, but not on the output drivers for the relays. Here's the (cut-down) schematic... The AC comes in, gets rectified and regulated to 12VDC. That's supplied to the ULN2003 which SHOULD drive the relays accordingly (along with an LED to show the status) For some reason, the reg heats up; the LED's don't change state; nor does the relays. There's no shorts that I can find on the PCB, so I'm pretty sure the PCB is correct. Removing the relays makes no change. Do any of the hardware wizards spot whatever the dumb mistake is that I've done? It's got me a bit baffled and I'm now in head-scratch mode.......   (PS: RLY2 to RLY6 is just a repeat of the RLY1 circuit) Edited 2024-12-04 16:18 by Malibu John