RG Keen's latching relay driver for bypass switching

timhulio · Post by **timhulio** » 11 Jun 2010, 15:56

I'm attempting to build this one:

I've used a 4069 rather than 4049 IC.

Here's my layout based on the above schematic:

Here's what it looks like:

This is the relay I'm attempting to use:
http://uk.rs-online.com/web/search/sear ... 587#header

The problem, quite simply, is that the relay does not switch. The flip flop works because the LED goes on and off. When switching there is a pulse of 0.2V but this isn't enough to switch the relay.
Does anyone have any experience of this schematic or tips?

pz · Post by pz » 11 Jun 2010, 16:07

Try to increase the two 0.1uF caps (C2 & C3).

timhulio · Post by **timhulio** » 11 Jun 2010, 16:30

I doubled these to 0.2uF but nothing.

pz · Post by pz » 11 Jun 2010, 17:00

You need more, like 1uF. It worked when i tried it a few years ago.

Fender3D · Post by **Fender3D** » 11 Jun 2010, 17:07

timhulio wrote:I doubled these to 0.2uF but nothing.

Caps will do nothing if you do not connect the relays + tip to V+

timhulio · Post by **timhulio** » 11 Jun 2010, 17:54

Fender3D wrote:Caps will do nothing if you do not connect the relays + tip to V+

Yes, using the relay I have, 'set' and 'reset' would be reversed. But it should still work, no?

timhulio · Post by **timhulio** » 11 Jun 2010, 19:02

pz wrote:You need more, like 1uF. It worked when i tried it a few years ago.

Bah. I've just tried it with a couple of 1uF non-polarised caps. Nothing doing.

I don't suppose you can remember which relay you used, or have a pic of the circuit you built?

timhulio · Post by **timhulio** » 11 Jun 2010, 22:00

Fender3D wrote:Caps will do nothing if you do not connect the relays + tip to V+

Ah I finally got it! See the revised layout at the top. This works nicely!

Thanks very much for your tips guys

pz · Post by pz » 12 Jun 2010, 06:53

timhulio wrote: Bah. I've just tried it with a couple of 1uF non-polarised caps. Nothing doing.
I don't suppose you can remember which relay you used, or have a pic of the circuit you built?

I was using NEC EA2-5T relays and with 100n it did work but not everytime, sometimes the relay didn't catch the pulse so i made the period longer by increasing the capacitors value.
But, it wasn't your case, as Fender3D pointed out

Mierdadepollo · Post by **Mierdadepollo** » 10 Sep 2010, 00:40

Will this circuit work with a latching DPDT relay like the one attached to this post? (or any other DPDT latching relay, for that matter)

If not, what differences could exist in two DPDT latching relays?

By the way, on the specs sheet of the relay there's some info:
Average current transmitted: (<- loosely translated)
DC 24V 2A
AC 120V 1A

It also says it's got a 12Vcc bobin.

ppluis0 · Post by **ppluis0** » 10 Sep 2010, 04:23

HI !!!! (I like the nickname you have chosen...

)

You can drive any normal relay (non latching type), merely replacing the upper 0.1 capacitor by a wire and driving the only coil (the upper one in the diagram) during the time that the effect is engaged.

In this manner the momentary switch acts as a toggle, and the transistor is closed at the same time that the led glows.

But the use of a conventional relay is not recommended if you plan use you stompbox with batteries. The latching type take tiny amounts of energy during the set or reset action and the conventional draws current all the time they're activated.

Cheers,
Jose

rasta_maleek · Post by **rasta_maleek** » 16 Mar 2011, 11:42

timhulio wrote:I'm attempting to build this one:

I've used a 4069 rather than 4049 IC.

Here's my layout based on the above schematic:

Here's what it looks like:

This is the relay I'm attempting to use:
http://uk.rs-online.com/web/search/sear ... 587#header

The problem, quite simply, is that the relay does not switch. The flip flop works because the LED goes on and off. When switching there is a pulse of 0.2V but this isn't enough to switch the relay.
Does anyone have any experience of this schematic or tips?

did you feed the relay with 9 volts?
it will be supplied with 5v, isn´t it?
thanks a lot

coldcraft · Post by **coldcraft** » 16 Mar 2011, 15:29

i was just wondering how to do this! thanks for doing the heavy lifting and confirming it.

rasta_maleek · Post by **rasta_maleek** » 10 Sep 2011, 06:33

hi all.
I did the relay driver with other relay type.
But i don´t know if it is adecuate to the proyect.
It´s a NEC EA2-5TNJ, 5v, dual coil, latching.

rasta_maleek · Post by **rasta_maleek** » 10 Sep 2011, 06:35

of course it works.
I will post the layout son, i´m fixing some errors

johnk · Post by **johnk** » 19 Oct 2014, 08:28

sorry for bringing up a very old thread, but I built this one today and it works perfect with the exception of the led being lit when in bypass mode, and off when the effect is engaged.
what's up with that? if I could correct that, it would be perfect.

Post by **The G** » 19 Oct 2014, 11:39

Reverse the LED and connect it to +V instead of ground.

johnk · Post by **johnk** » 19 Oct 2014, 14:36

thanks!
that did the trick and it works perfect now.

johnk · Post by **johnk** » 13 Feb 2015, 02:33

I've now built quite a few of these and they all work great.
I also heard that a Panasonic TQ2-L2-5V works in it but I built one with that relay and although the LED switches on and off, the relay doesn't work at all. it's just stuck in one position.
I experimented with different cap values but to no avail. does anyone have any ideas as to why it doesn't like the TQ2-L2-5V?

jwpartain1 · Post by **jwpartain1** » 13 Feb 2015, 14:47

Try increasing the value of both of the caps across the collector-base of the two switching transistors.

RG Keen's latching relay driver for bypass switching [SOLVED]