Wierd issue diagnostic help

[Funkalicousgroove]

What is your power transformer? the 5v tap should yield about 7v DC rectified FWB, and should be plenty of juice for 4 relays and a couple LED's

[greiswig]

What is your power transformer? the 5v tap should yield about 7v DC rectified FWB, and should be plenty of juice for 4 relays and a couple LED's

You're right...this isn't making sense to me now. I've attached the Brownnote schematic of the way it works here. I verified that the DC voltage starts out above 14V, and when one relay is tripped it drops it to about 11V. This continues down until, at 4 relays tripped, the DC voltage is about 7.5V.

All the while the 5.4VAC at the entrance to the rectifier circuit remains virtually unchanged. Whatsgoinon? I sense a learning opportunity at hand!

[mlp-mx6]

Well, first of all, the rectification Brandon mentioned and the schematic you posted are not the same at all. If you bridge-rectify the 2 5V wires you should get a solid 7V or so. What you are showing is a voltage doubler circuit, which has higher output voltage (to start with) but VERY poor regulation.

Can you do a FWB (full-wave bridge) rectifier circuit with what you have?

[greiswig]

Well, first of all, the rectification Brandon mentioned and the schematic you posted are not the same at all. If you bridge-rectify the 2 5V wires you should get a solid 7V or so. What you are showing is a voltage doubler circuit, which has higher output voltage (to start with) but VERY poor regulation.

Can you do a FWB (full-wave bridge) rectifier circuit with what you have?

Didn't know it was a doubler! Thanks for that. Yeah, if I added another pair of diodes and moved a couple of things around, (correct me if I'm wrong) I'd have a full wave rectifier. As you said, that should get me a little over 7V. Which would be fine if I then put a regulator on it and ran 5V relays, but that's a fair amount of work. The 12V relays I have are working fine, even with the voltage drop.

And it seems like a red herring: I disconnected the positive of this power supply, connecting a 12V battery instead. The same popping is still happening.

And I also replaced that cap that I suspected. Although the voltage oddity that I'd seen there is gone, the popping remains.

The switch seems to be firmly planted to the chassis. I'm kind of back to square one. Should I undo all the grounds, sand the chassis, and reconnect? Does a bad ground still seem like a likely cause?

[Structo]

I got my 8v regulated power supply and relay boards from Deric Dobesh.

It uses a full wave rectifier, 5 470uf electrolytic filter caps and the 511-L7808ABV (mouser) regulator.

He told me this would power 3 relays with no problem.
But I am just using 2 relays and the leds are in parallel to the relay coils.

Maybe Deric will drop by and lend a little insight to his design.

[mlp-mx6]

And it seems like a red herring: I disconnected the positive of this power supply, connecting a 12V battery instead. The same popping is still happening.

And I also replaced that cap that I suspected. Although the voltage oddity that I'd seen there is gone, the popping remains.

The switch seems to be firmly planted to the chassis. I'm kind of back to square one. Should I undo all the grounds, sand the chassis, and reconnect? Does a bad ground still seem like a likely cause?

I would suggest putting a very high-value resistor (10M, 22M) across the switch contacts of the relay that is popping. (not the relay power, but the actual circuit you are switching) This will let the cap(s) charge so there is no sudden rush of current into the cap, which is usually what causes popping anyway.

[talbany]

Popping issue is generally related to a DC off set at the relay coil..
a number of things can cause this..Looking @ the schematic your way under filtered.. Like Funk said at least 1000uf I use 3300uf..
If you use a voltage doubler the transformer needs to be able to handle the added current capacity to keep the voltage constant otherwise you can get some wild voltage swings, longer recovery time and a hot transformer...Not to say that thats what your seeing but sure is a symptom...
I used to use 12v relays and since went with the 6v ones.. Less chance of the offset with the lower voltage at the coil..To me a voltage doubler on a relay circuit seems kind of useless unless you want a brighter led (if someone knows something I don't) unless you get a box of surplus 12v relays and 6V transformers I don't see the benefit... I full wave rectify 6v ac=8.4v filter it 3300uf and regulate it..and try to ground the footswitch @ the same point as the regulators ground...

Good Luck


Tony VVT

[greiswig]

Thanks, Tony. And everyone else who's contributed ideas, for that matter! But if I hook up a 12V battery instead of that shaky, poorly-regulated supply, it doesn't make any difference as far as this popping behavior goes.

Here's the thing: my gut tells me that it has to be significant that the popping GOES AWAY after toggling the OD relay a few times.

You can either do this right after turning standby on, or you can wait a few minutes, but in either case the first time you flip that switch is going to be the loudest pop. After some number of times, the popping noise is back to the normal, very tolerable level that it has been at before this past weekend.

[greiswig]

[quote="mlp-mx6
I would suggest putting a very high-value resistor (10M, 22M) across the switch contacts of the relay that is popping. (not the relay power, but the actual circuit you are switching) This will let the cap(s) charge so there is no sudden rush of current into the cap, which is usually what causes popping anyway.[/quote]

I'll give that a go. It still seems odd that it would suddenly start doing this out of the blue, but at this point I am eager for a practical solution!

[talbany]

I would suggest putting a very high-value resistor (10M, 22M) across the switch contacts of the relay that is popping. (not the relay power, but the actual circuit you are switching) This will let the cap(s) charge so there is no sudden rush of current into the cap, which is usually what causes popping anyway.[/quote]

Definiately worth a try!! Sorry I couldn't be much help..


Tony VVT

[greiswig]

Well, putting an 11M resistor across the switch contacts helped, but all it did was attenuate the effect. Maybe that's good enough, but it makes me think there's something wrong elsewhere and I'm just putting a bandaid on it.