More relay issues

[Bob-I]

I have 2 relays in my 3 channel amp. Relay one switches between the Fender and Dumble preamp, relay 2 switches the Dumble from clean to OD.

The issue I'm having is that the voltage drop that is caused by one activating can deactivate the other. It seems to drop below the threshold of activation.

I thought it might be that my power supply was marginal at 4V for 6V relays so I reengineered it to a voltage doubler at 7V.

How can I run 2 relays off one supply? Or will I simply have to build 2 supplys?

[llemtt]

Bob

One supply once properly dimensioned is ok for lots of relay (I usually run 4-5 in my amps), the limiting factor is the current available from the transformer. Your relays should have a spec saying how many mA they draw at nominal voltage, just sum them to have the total current draw then ensure that the trasformer gives at least two times that current at nominal voltage.

The problem with your supply seems more with capacitors, you have to use bigger ones! 4700uF is ok, 1000uf is acceptable.

The two stage filtering is another key factor, the 150 resistor drops lot of voltage as you add more relays, reduce the resistor (with 4700uF caps you don't even need the second stage).

teo

[Bob-I]

Bob

One supply once properly dimensioned is ok for lots of relay (I usually run 4-5 in my amps), the limiting factor is the current available from the transformer. Your relays should have a spec saying how many mA they draw at nominal voltage, just sum them to have the total current draw then ensure that the trasformer gives at least two times that current at nominal voltage.

The problem with your supply seems more with capacitors, you have to use bigger ones! 4700uF is ok, 1000uf is acceptable.

Ok, I used these because I had them. I'll try some 1000uF.

The two stage filtering is another key factor, the 150 resistor drops lot of voltage as you add more relays, reduce the resistor (with 4700uF caps you don't even need the second stage).

teo

That's really only one stage, remember it's a voltage doubler so the first pair of caps are in the doubler. I'll drop the resistor down.

Thx

[skyboltone]

Hi Bob:
I'm with Teo, loose the resistor altogether. The 6 volt relays won't smoke at 7 volt.


Dan

[Bob-I]

Hi Bob:
I'm with Teo, loose the resistor altogether. The 6 volt relays won't smoke at 7 volt.


Dan

The resistor is for filtering. I modeled this with the duncan PS modeler and without the resistor and 3rd cap there was terrible ripple.

[Bob-I]

Damnit.... I can't figure this out for the life of me.

I removed the resistor and second stage filtering, then had too much voltage so I went to the simplist PS I could. 6VAC -> Bridge -> 1000uF cap.

Now I have a solid 7VDC with some ripple that doesn't seem to matter. The relays are still not functioning correctly, almost randomly. I know the switches are working and voltages being applied because the lights work and I've measured the voltages.

So why the intermittant relays switching?

I'm at a loss.

[skyboltone]

Can you verify by watching the multimeter (set the hold voltage feature low) that they are dropping out on low voltage and not NO voltage?

The only other thing I can think of is that maybe sharing a wire to the foot pedal has something to do with it? What form factor are the foot switches? That is to say, SPST DPST? Is there some kind of way that you've wired them so that you momentarily apply a short circuit to the relays power supply while picking up the other relay?

What size is the wire to the foot switch? Is plain voltage drop due to undersized wire the problem?


Just shooting from the hip here.

Dan

[Bob-I]

Can you verify by watching the multimeter (set the hold voltage feature low) that they are dropping out on low voltage and not NO voltage?

I'll give that a shot.

The only other thing I can think of is that maybe sharing a wire to the foot pedal has something to do with it? What form factor are the foot switches? That is to say, SPST DPST? Is there some kind of way that you've wired them so that you momentarily apply a short circuit to the relays power supply while picking up the other relay?

No foot switchs, I removed them to troubeshoot. I'm using mini SPDT switches on the panel. I wonder if they're shorting before switching.

What size is the wire to the foot switch? Is plain voltage drop due to undersized wire the problem?

22AWG to the panel, no more than 4" long. The neutrals are tied together at the PS and nothing is grounded as this adds noise.

Just shooting from the hip here.

Dan

Thx Dan, I appreciate you taking to time to think it through.

[Bob-I]

What size is the wire to the foot switch? Is plain voltage drop due to undersized wire the problem?

I think I found it... not undersized wire but you led me to the issue. It's the LED's dropping the voltage. I disconnected the LED's and resistors and it appears to be fine now.

Just shooting from the hip here.

Dan

You hit the mark that way. Thx!!

Now I need to work out how to power the LED's without screwing up the relays.

[skyboltone]

Well, Mat was working on a scheme using a 9 volt battery and a 2.2k current limiting resistor to run the leds. But he ran out of relay contacts so I put them in parallel with the relay coils.

Wonder how he's comming along, Ha! I probably got him screwed up!

Dan

About that #22 CMA of #22 is 642.4 (Circular Mil Area) K for cu is 12

I X E X K X 2L .100Ax5x12x20
---------------- -------------- =.23v Insignificant
CMA 642.4

All this is predicated on a ten foot cord to the pedal, 100 ohm coils and a 5 volt supply. The only time this would be significant is if the coils spike a Big current sink. Then it might make a difference.

[Bob-I]

Well, Mat was working on a scheme using a 9 volt battery and a 2.2k current limiting resistor to run the leds. But he ran out of relay contacts so I put them in parallel with the relay coils.

Wonder how he's comming along, Ha! I probably got him screwed up!

Dan

I read that thread, made since to me.

About that #22 CMA of #22 is 642.4 (Circular Mil Area) K for cu is 12

I X E X K X 2L .100Ax5x12x20
---------------- -------------- =.23v Insignificant
CMA 642.4

The only part that mattered to me was the "Insignificant" part

I have a bunch of this 22AWG/300V solid core wire so I'm always looking for a use for it.

All this is predicated on a ten foot cord to the pedal, 100 ohm coils and a 5 volt supply. The only time this would be significant is if the coils spike a Big current sink. Then it might make a difference.

Yepper. I upper the current limiting resistors on the LEDs, 220-> 1K and reconnected the footswitch. Everything's working fine now. The LED's are a tad dull but the switching is solid.

Thx.