Using a BOSS-pedal's flip-flop to drive a relay

[jakenold]

Hi guys,

I've been sitting for some time now, trying to make this work, but I just can't. I've managed to build a flip flop that can turn the relay on and off, but how do I use the one currently in my BOSS effects? I feel it would be silly to add another circuit if I can just insert the relay in the current one.

It's an Omron 5V 180ohm relay. Where do I connect it?

Thanks!

Jake

[km-r]

i think the boss' flip-flop may not be able to drive the relay... use a transistor to toggle the relay... i think the signal output of the boss flipflop is from ground to 1/2v+
or use a SCR???

[miqbal]

Replace the indicator LED with the relay???, and jumper the Zener Diode and the current limiting resistor (usually the3.9k). Let's pray....

[Ben N]

There is a simple mosfet relay/indicator LED driver here (in figure :
http://www.geofex.com/Article_Folders/fxswitchr/fxswitchr.htm

I imagine that mosfets are good because they can provide enough current to drive the relay; probably a bjt or an opamp would work too. In any event, it shouldn't be too hard to find a relay driver schematic. Be sure and post when you come up with something that works--I'd bet a lot of people would have a use for that.
Ben

[jakenold]

I must either be retarded, insane or both - I cannot get this to work!

If someone has the knowledge how, will they please elaborate? I even tried to get some of the transistor flipflops on Bill Bowdens site to work and I couldn't! I double checked everything.

It's super annoying - I've built more than 100 effects and 3 amps, but this is apparently rocket science to me!

Jake

[km-r]

wait... are you trying this out for true bypass?? you should know that relays will POP if not for some additional components...

[Rob Strand]

> I must either be retarded, insane or both - I cannot get this to work!

Perhaps not.

One thing you might be overlooking is how much base current you need to drive the relay.

I'm not sure what you have tried but getting the Boss flip-flop to drive the relay directly will need a lot of changes.  If the flip-flip drives another transistor, like many of the Boss pedals do to drive the LED, then it should work.  The Boss pedals use a high value base resistor, like 1MEG you will need to reduce that.

A 5V 180ohm relay requires 28mA.  You will need a base resistor at least 47k, preferably 10k-22k.  Given the Boss flip-flop has 56k pullups then it's going to struggle to drive the relay drive transistor.  So try dropping one of the 56k flip-flip resistors to 10k and use another 10k to the base of the relay transistor.

Second thing is running the relay off 9V.  The simplest way to do this is to add a series resistor = (9-5)/28mA = 140ohm, so use 150ohm.

[jakenold]

Thanks Ron, looks as if there is still hope for my poor mind.

I tried rebuilding the relay with the relay-driver at Bill Bowdens site, and every time i shorted the switch, the relay would start closing and opening like it was hooked up to an oscilator! I'll try your tips, and return what I find.

Thanks!!

[R.G.]

The Boss flipflop simply doesn't have the drive capability.

Try running an external darlington or BS170 MOSFET from one output of the relay and having that pull the coil current.

[Ben N]

> I must either be retarded, insane or both - I cannot get this to work!

Perhaps not.

LOL--that's the benefit of the doubt for you!  Perhaps not...  Sheesh

[jakenold]

The Boss flipflop simply doesn't have the drive capability.

Try running an external darlington or BS170 MOSFET from one output of the relay and having that pull the coil current.

I plan on bridging the bypass-system - can I use the PCB-layout of a common BOSS effect to accommodate the circuit your a describing? The less I have to add into those tiny boxes, the better!

Jake