Relay bypass without a microcontroller

2/17/2018

I've seen alot of people wanting microcontroller-free relay bypass boards. There's a few designs out there, but most of them seem overly complicated, so I designed this one. It uses two 2N3904 as a simple switch flip flop and debouncer. It's not perfect (the occasional mistrigger happens) but overall it works pretty well for such a simple design. :)

I'm selling a Relay Bypass PCB in the shop for an improved version (with solid debouncing) with a smaller size than the vero version. Check it out. :)

12 Comments

twebb6778

11/11/2020 04:17:00 am

I've built two of these but I'm struggling to get them working. My effect is working correctly, the relay itself is switching, and the LED is operational, but it doesn't seem to pass signal. I'm using a Takamisawa NA12W-k relay and 2n2222 transistors. Is there possibly a schematic available to help me verify my work?

Fredrik Lyxzén link

11/18/2020 03:45:50 am

Send me an email, and I'll sent your the schematic. Best regards / Fredrik

Matt

3/14/2021 02:34:00 pm

Is there a way to alter this layout to use a 5v relay. I have recently purchased a bunch for another build. I only needed one but it was cheaper to buy more

Fredrik Lyxzén Parasit Studio link

3/15/2021 04:14:40 am

Hi Matt,

The only way you could use this with a 5v relay is that the board recieves 5v instead of 9v. You could make a small little daughterboard with a 78L05 voltage regulator (in a to-92 size) that will take 9v and give you the 5v needed.

Matt

3/27/2021 06:26:33 pm

Thank you for the reply. Is this for a latching or non latching relay?

Fredrik Lyxzen link

3/29/2021 08:26:38 am

It's for a non-latching relay. The transistors act as both a button debounce and latching flipflop that controls the state of the relay.

Adam M

7/26/2021 08:43:26 pm

Great little board. Easy build and works. One question/ comment. The schematic says "when turning a effect on it will toggle back to bypass if you hold the switch too long." I found this to be true but it's definitely less than 1 second and it's back to bypass. Probably close to .5 seconds holding the switch and it jumps back. Is there any way to extend this time? Thanks!

Fredrik Lyxzén link

8/27/2021 07:35:09 am

Increase the value of the electrolytic (4.7uF) to extend the time it takes before it switches back.
/ Fredrik
PS. Didn't see you post until now, so I apologize for the super late reply.

Robert

12/1/2021 07:00:52 am

Would this work in place of a DPDT that a Klon circuit needs, like this one here:

http://tagboardeffects.blogspot.com/2014/07/klon-centaur-silver-edition.html?m=1

Thanks!

André

12/6/2021 06:00:49 pm

Hello, how is everything? Does this relay work?

Módulo relé de sinal 10 pinos-takamisaw
A12W-K 12VDC
https://a.aliexpress.com/_mLl4Gqw

Thanks

Anjang

12/12/2021 06:43:23 pm

I try with regulator 78L05 and 5vdc relay, but it doesn't click the relay, sound like its back to off faster.. so what part i must to modified ??

Matt

2/11/2023 08:03:33 pm

Hi!
Do you by anychance have a schematic available for the PCB version of this? The build doc doesnt seem to have one. Thanks!

Relay bypass without a microcontroller

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