Using TinyG with SSR Relays.. Not Turning On Relays? page 2

Update... Yes we are looking into this! I think the worst come to worst case for TinyG v8's is we might need to pull a resistor off the board for that line. Please hold up from doing anything yet (meaning messing with the board :) we are working on getting a solution tested and up on the wiki. Those relays should work just fine with the voltage that the xmega can supply so there is hope.

Riley

The v8 outputs are about 3v to 3.2v from the 3.3v processor. On the v9 (not yet released) we have provided a way to generate 5v outputs, but that doesn't help you much on the v8. There are 3 ways I can think of to drive the SSR from a v8:

1. Use an external level shifter. The 74LS125 or 126 are good chips for this. Tie the Vcc to 5v and drive the input from the 3v signal. Make sure the enable is set hi or lo depending on which chip you are using.

2. Find an SSR that actually meets its 3v spec. Seems to be easier said than done.

3. Cheat the TinyG board by voiding the warranty. It's possible to drive the on-board components at up to 3.6v (MCU and stepper drivers). If you change out the voltage setting resistors on the switching regulator you can fiddle with the voltage to - say - 3.5v. This might provide enough lift in the outputs to actually drive a marginal relay. I don't recommend this - it's very dicey. One slip and you fry the entire board. But it's possible

I think option 1 is the best.

I don't have a breadboard recommendation. There might be some out there. I'd probably just get a DIP version of the chip and breadboard it. You can get 5v off the board - check the schematics. The 125/126 have 4 buffers, so you can do all the pins it you need to.

Not a bad question. Yes, this setup should work on anything that has up to about a 10 nanosecond rise time requirement. Plenty fast for the PWM channel!