powering 5v relays with the filament supply.

[BobW]

Check this link:

http://ampgarage.com/forum/viewtopic.php?t=1473&start=0

The 12V relay power circuit shown in the schematic uses a voltage doubler and the filament voltage as a source. However the schematic doesn’t show the shunt diode across the coil. I’ve used this amp for over 50 gigs and No noise issues using this circuit.

Bob,

Your circuit may work okay for a single OD relay, but it suffers from some the problems Andy describes - it has to be isolated from the rest of amp, no reference to a common ground on the coil side, poor regulation. If you cascaded a couple more relays, in particular a PAB relay or mid boost relay which are in more sensitive areas of the circuit, I bet it would buzz.

My particular layout was not built with or intended to use multiple relays, and suggest you go back and read the schematic notes, you will see the doubler circuit is floating (ground isolated).

[odourboy]

Check this link:

http://ampgarage.com/forum/viewtopic.php?t=1473&start=0

The 12V relay power circuit shown in the schematic uses a voltage doubler and the filament voltage as a source. However the schematic doesn’t show the shunt diode across the coil. I’ve used this amp for over 50 gigs and No noise issues using this circuit.

Bob,

Your circuit may work okay for a single OD relay, but it suffers from some the problems Andy describes - it has to be isolated from the rest of amp, no reference to a common ground on the coil side, poor regulation. If you cascaded a couple more relays, in particular a PAB relay or mid boost relay which are in more sensitive areas of the circuit, I bet it would buzz.

My particular layout was not built with or intended to use multiple relays, and suggest you go back and read the schematic notes, you will see the doubler circuit is floating (ground isolated).

Exactly! As long as we're on the same page.

[BobW]

Bob,

Your circuit may work okay for a single OD relay, but it suffers from some the problems Andy describes - it has to be isolated from the rest of amp, no reference to a common ground on the coil side, poor regulation. If you cascaded a couple more relays, in particular a PAB relay or mid boost relay which are in more sensitive areas of the circuit, I bet it would buzz.

My particular layout was not built with or intended to use multiple relays, and suggest you go back and read the schematic notes, you will see the doubler circuit is floating (ground isolated).

Exactly! As long as we're on the same page.

We are. My thoughts are since the relay circuit is not part of the signal path, but should be noise free, this is an area that doesn't necessarily need to follow HADs exact design. FWIW, my #124 build uses HADs circuit.

[wjdunham]

FYI, on the circuit reference in my previous post, I gave it a try last night, and it worked just fine, both relays fire and no noise issues. I really wanted to stay away from isolated return for the relays, as I feel it's too easy to make a mistake and ground something, or if I ever sold the amp, have the new owner blow something up.
I need to try it out for a few hours, my previous half-wave approach worked when the amp was cold, but after things heated up, couldn't fire both relays with the footswitch. (edited - I now have 8V on the relay supply, vs. 4V with the previous. Omron 5V relays don't need the full 5V to fire, but the circuit was very marginal).
This seems like an ideal circuit if you want to use the center tapped filament windings to generate the relay voltage and still have everything referenced to chassis ground.
Bill

[Structo]

Bill, I remember when I was installing my relays and footswitch stuff on my D'lite, that there were some guys having trouble with powering three or more relays plus the LED's.

If I recall, one of the things that really helps out is to power your LED's on the pedal separately so they are not in series with the relay coils.
The original design of the D'lite had them in series.

Also, the type of relay is very important as there are some low signal/ high sensitivity ones that work very well.
We want that OD relay very robust and able to stay on for long periods of time without failing or getting too hot.

Deric helped me out at the time and I bought some pcb's from him.

The relays he recommended and that others use are the
Omron 5v, Mouser # 653-G5V-2-H1-DC5

Since my D'lite has a 5v rectifier tap on the PT, we used that for the relay power supply.
Deric came up with the 8v regulated supply and it works great.
This power supply uses a voltage doubler to make around 10v then it regulates it at 8v.
I currently have three relays and two LED's working with this setup.

This is the 8v regulator.
511-L7808ABV

This is the TO-220 heat sink used.
140-PM2A104K

The sockets we used are the 575-199316 16 pin DIP socket.
This is a great socket and really grabs the relay pins good.
When you look up that number you will see they also make one with gold plated contacts if that is your thing.

Then the use of the 5 pin DIN connector on the back works well.
I think I used CAT 6 cable for the lead on the pedal.

[ChrisM]

Relays should never run hot. Yes if you put more voltage then speced into them they run hot. Like 8V into 5V, but that doesn’t make sense to me.

I don’t know why everyone makes a big deal over this. Get a DC voltage, regulate it, filter it before and after the regulation. Keep your LEDs in parallel with the relay. Done.

[odourboy]

Relays should never run hot. Yes if you put more voltage then speced into them they run hot. Like 8V into 5V, but that doesn’t make sense to me.

If you run your LEDs in series with your relays (which is what most of us do) then you're dropping almost 2V across the led. So 8V is closer to 6, Well within the 7.5V max spec these relays are rated at.

[ChrisM]

Why do that though? LEDs forward voltage drop vary some brand to brand, type to type. Putting the LED in parallel you don't have to worry about what type your using. Also if the series LED fails then your relays wont be doing anything, not the case for parallel.

[odourboy]

Why do that though? LEDs forward voltage drop vary some brand to brand, type to type. Putting the LED in parallel you don't have to worry about what type your using. Also if the series LED fails then your relays wont be doing anything, not the case for parallel.

I've never figured out how to run the LED in parallel with the relay when the relays are in the chassis and the LEDs are in the foot switch. I usually use 4 relays/foot switches/LEDs and a five conductor cable.

[mr_hankey]

Sorry abut resurrecting this old thread, but I figured it wasn't worth its own topic.

[img:800:423]http://i.imgur.com/4xWoz6a.jpg[/img]

I've wired my relay supply according to this schematic. The two 5VAC leads come from the PT. As I don't want to have to run two wires to my relay and into my footswitch, can I just ground the negative output and use the one 5V wire? The outputs measure +/- 300mV above ground at the moment.

[FUCHSAUDIO]

You're better off making a doubler, not using a bridge, use the chassis as a heatsink. You get about 11 volts, then regulate down to 8 volts. We use 8 volt regulators and 5 volts relays with an LED (parallel to a 100 ohm resistor) to run the relays. Problem with this circuit is that the regulator could drop out of regulation or not have enough ripple rejection, if the input/output voltage gets too close. Most chip regulators like 3 volts or more, and low line voltage or high current draw would load things down and it could get noisy. Relay coils radiate hum nicely if you send ripple into them.

This circuit will support plenty of relays (depending on the source voltage and current), but the extra 5 volt in/out of the regulator allows for the voltage to drop a few percent and still stay in regulation and have the relays work quietly and hum free. The LED can be in the pedal or in the amp. Most guys like the LED in the pedal obviously. If no LED, use a 30-Ohm 1/2 resistor to limit current with most relays. Some 5V relays can take 8 or ten volts and not care, some heat up or current increases, so the relay type and brand DO matter.

I run as many as ten relays in the Tripledrive, with no issues, and a small heatsink.