Attiny85 used for relay bypass won't work with Strymon power supplies

[patrick398]

Hi,

I wonder if anyone else has noticed this strange behaviour when using microcontrollers to control bypass relays when they are powered with Strymon power supplies. I've heard that Strymon supplies ramp power from 0-9v on startup and this seems to fool the uC's into thinking there's no juice. I can repeat this behaviour with my bench supply, if i plug the pedal in and then turn the voltage up from 0-9v the uC's dont function...seems very strange and i can't find a solution 

Any ideas?

[niektb]

Check how the reset pin is wired, you should have a little RC filter between the voltage rail and the reset pin (to delay the reset coming up)

[patrick398]

Interesting, I hadn't heard that and I just leave pin 1 unconnected. What values would you suggest?

Thank you!

[niektb]

I have very good experiences with these values: 10k, 100nF and then a 1N4148 anti-parallel to the resistor (so pointing towards the power rails) (this is to make sure that on power-down the reset pin is discharged quickly and not through the 10k

[Sweetalk]

Check how the reset pin is wired, you should have a little RC filter between the voltage rail and the reset pin (to delay the reset coming up)

Had the same behavior with some circuits and this boards and the problem was this, the reset pin. I use a 10K pullup resistor, a 10uF cap and a diode, solved the ramp up problem.

[patrick398]

Fantastic, thanks guys, I'll will give this a go and play around with some values

[Buffalo Tom]

I have very good experiences with these values: 10k, 100nF and then a 1N4148 anti-parallel to the resistor (so pointing towards the power rails) (this is to make sure that on power-down the reset pin is discharged quickly and not through the 10k

Is this correct with 100nf from reset pin to ground?

[niektb]

Yess looks correct to me!