Needing a couple of SSRs, I cheaped out and bought a dual SSR board that had snubbers built in. It has the following connectors (Vcc, GND, CH1, CH2). Vcc supply and CH1&2 are 3-32VDC. The SSR board works fine. I will only use 1 channel (SSR) at a time and it consumes 18-25mA to activate one SSR.
The MCU I am using is a 3.3v system with a max of 15mA output.
I built the attached driver just using a single driver on a bread board and worked perfectly. I transferred to perf board with the dual and the SSR stayed on just with Vcc and GND (no input to the CH pins).
I figured it was my sloppy perf board that was the problem, so I etched a PCB, soldered it up, ensured I had not shorts/bridges and I have the same problem. I then realized I put in all the transistors in backwards. Flipped them all around and still have the same problem.
Writing this I wonder if I pulled the bases of the NPNs to ground through a R would help..
Anyone see anything I screwed up on?
My last resort is just to desolder the SSRs and activate them directly by sinking the current.
R1 and R8 just simulate the load to activate the SSR.
Thanks for your help.
-Dave
The MCU I am using is a 3.3v system with a max of 15mA output.
I built the attached driver just using a single driver on a bread board and worked perfectly. I transferred to perf board with the dual and the SSR stayed on just with Vcc and GND (no input to the CH pins).
I figured it was my sloppy perf board that was the problem, so I etched a PCB, soldered it up, ensured I had not shorts/bridges and I have the same problem. I then realized I put in all the transistors in backwards. Flipped them all around and still have the same problem.
Writing this I wonder if I pulled the bases of the NPNs to ground through a R would help..
Anyone see anything I screwed up on?
My last resort is just to desolder the SSRs and activate them directly by sinking the current.
R1 and R8 just simulate the load to activate the SSR.
Thanks for your help.
-Dave
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