Danelectro Rocky Road "Always on" question

blues123 · Post by **blues123** » 15 Dec 2020, 16:28

Hi,
I am in the process of rehousing a Danelectro Rocky Road.
So far, so good. Mods working, true bypass is working and the old flip-flop circuit now redundant , however, I still need to apply a momentary Ground to the HE83015 chip to activate the effect (using the old on/off monetary switch) after I have used the 3PDT true bypass switch .
What I would like, is for the circuit to be active on power up, so it is already in a state of readiness when I hit the new mechanical switch.
Please see schematic -

Dj_20.pdf: (72.79 KiB) Downloaded 70 times

Anybody got any ideas?
Thanks

mauman · Post by **mauman** » 15 Dec 2020, 17:15

Looking at the IC data sheet and your schematic, the original foot switch applies a momentary ground to PC1 and PC5, which are two bits of a bidirectional I/O bus, and apparently that serves as the start signal for the routine. I don't see a way to work around that, so the question is, what mechanisms are available to do that other than pressing the original switch?

What happens if you sustain the ground on those two pins indefinitely? If the routine starts and the pedal works, maybe you can just tie them to ground. Not elegant, and not likely to work, but possible. Or if you need a one-shot ground pulse of finite duration to start it, a 555 might serve, triggered by your 3PDT. Mike

deltafred · Post by **deltafred** » 15 Dec 2020, 17:43

Put a capacitor to ground from the pin and a pull up resistor to the supply.

This is often used as a "Power On Reset" in digital circuits that need the reset line holding low for a short period on power up.

At power up the capacitor will be discharged and so have zero volts across it. This will pull the input to ground. As it charges up through the resistor the voltage will rise until it exceeds the logic 1 value of the input.

Determine what values work reliably by substitution. If no suitable values are found then it is back to a switch.

blues123 · Post by **blues123** » 15 Dec 2020, 18:04

Mike, thanks for the info. I did try tying the on/off pin to ground which did keep the effect on, but it stopped the ramp up/down switch from working. 555 might be worth a go. Thanks for the idea.

Fred, I’m a really noob with digital, so thanks for the idea. Will give it a try.

Thank you both

mauman · Post by **mauman** » 15 Dec 2020, 18:05

Definitely try deltafred's solution before adding a 555! Mike

Danelectro Rocky Road "Always on" question [SOLVED]