Relay supply

[HiGain]

I've done a search and came up with lot's of interesting info...

Does this schematic look correct to you guys?

My main quesiton is which radio shack transformer to get and how to connect the leads.

Also, the wiring for the LEDs is incomplete. Any thoughts on how to complete it?

Thanks, Jake

[heisthl]

Get the transformer that has a 12VAC secondary (they have 2 choices - either will work). If the transformer has a center tap, just cut it or tape it off.
Put the LED/resistor in series with the switch (the 1K resistor will need to be changed to 150 ohms).

[ayan]

I've done a search and came up with lot's of interesting info...

Does this schematic look correct to you guys?

My main quesiton is which radio shack transformer to get and how to connect the leads.

Also, the wiring for the LEDs is incomplete. Any thoughts on how to complete it?

Thanks, Jake

In addition to what was already mentioned, Dumble hardwired the "+" side of the supply to the relays and switched the ground off or on. Strictly as shown, things will really not work at all.

Suggest that you: (1) At the "+" side of the supply, connect the 1K resistors (not sure why you would use 150 ohm one, you might smoke the LEDs that way with a 12V supply) and run to the "+" terminal of the LEDs at the footswtich; (2) the ground wire from the footswitch will be tied to the "-" end of the relay coils (at the footpedal switch in the back panel of the amp); (3) then, the switches (manual and foot, which are wired in parallel for each relay) will toggle the "-" side of that conenction to ground or open circuit.

Gil

[heisthl]

not sure why you would use 150 ohm one, you might smoke the LEDs that way with a 12V supply

Gil

I may have left the wrong impression, I used a 150 ohm/LED parallel in series with the switch. The 150 ohm value is kind of universal to whatever relay types might be used. It save having to run additional wires to the footswitch (which is what HAD did - separate wires for LED +).

[HiGain]

double post...

[HiGain]

OK... Here's another draft. I still think I have it wrong, as the Panel Switches have to be on for the foot switches to work.

What is my little brain missing here?

Thanks,

Jake

[heisthl]

Try it this way:
EDIT - REMOVED INCORRECT SCHEMATIC - See corrected version below.

[ayan]

OK... Here's another draft. I still think I have it wrong, as the Panel Switches have to be on for the foot switches to work.

What is my little brain missing here?

Thanks,

Jake

It looks correct. However, I would put the 1K resistors at the board... why? So that if there is a short downstream from there somewhere, you don't burn out your 12V transformer.

Gil

[ayan]

Try it this way:

I paologize if I am completely off base here, but I really don't understand why you would do as suggested on the schematic.

1. The LEDs see the full 12 VDC, and unless you buy the ones with a dropping resistor included, you will burn them out. LEDs really work on a current basis... not enough of it and they will not light up, too much of it and they will go.

2. Also, your resistors need to be 2W as shown, since they too see the full 12 VDC (150 ohms dissipate 12 X 12/150 = 1W). Why put that additional strain on the little transformer? See, the RS thingie is rated at 12V 0.45A, which spells 5.4W max... you'd be using up 4 W on the resistors alone. The voltage regulation puts an additional stress on the supply, and then the relay coils and the LEDs will need some power too.

I must really not be understanding something, because I see no single good reason to use this scheme.

Respectfully,

Gil

[heisthl]

I paologize if I am completely off base here, but I really don't understand why you would do as suggested on the schematic.

1. The LEDs see the full 12 VDC, and unless you buy the ones with a dropping resistor included, you will burn them out. LEDs really work on a current basis... not enough of it and they will not light up, too much of it and they will go.

2. Also, your resistors need to be 2W as shown, since they too see the full 12 VDC (150 ohms dissipate 12 X 12/150 = 1W). Why put that additional strain on the little transformer? See, the RS thingie is rated at 12V 0.45A, which spells 5.4W max... you'd be using up 4 W on the resistors alone. The voltage regulation puts an additional stress on the supply, and then the relay coils and the LEDs will need some power too.

I must really not be understanding something, because I see no single good reason to use this scheme.

Respectfully,

Gil

I was about ready to call you crazy until I actually looked at the schematic. I had cut and pasted onto his and put the resistor/LED pair(s) in the wrong place. The reason for doing it this way is you can get a lot more switches on the same 5 wire cable and still have LED indicators. The LEDs just see the drop across the resistor so you can adjust its value for desired brightness (bigger = brighter). You might want to bump up the supply slighlty by putting a couple of diodes on the regulator ground to get 13.2 volts. The .45Amps is plenty to run this circuit if you're using efficient (read low power draw) relays.

[heisthl]

Better way to draw it:

[ayan]

I was about ready to call you crazy until I actually looked at the schematic. I had cut and pasted onto his and put the resistor/LED pair(s) in the wrong place. The reason for doing it this way is you can get a lot more switches on the same 5 wire cable and still have LED indicators. The LEDs just see the drop across the resistor so you can adjust its value for desired brightness (bigger = brighter). You might want to bump up the supply slighlty by putting a couple of diodes on the regulator ground to get 13.2 volts. The .45Amps is plenty to run this circuit if you're using efficient (read low power draw) relays.

No problem on the crazy thing. What I don't like about that arrangement is that the LEDs are on when the relays are on, and they are in series, so whatever voltage drop there is across the LEDs will be subtracted from the power supply, so you might have some ringing problems with the relay coils.

The way to get it all working well, IMHO, while saving wires would be to place the LED in series with a resistor and the coils. The resistor is sized such that there is not enough current to energize the relay coils when the circuit is closed, but the LEDs will light up. Then, if you short circuit the series of the LED and resistor, the LED will turn off and the voltage across the relay coil will be the full power supply value, so the relay will be activated and not prone to ringing. In this scheme, the LEDs light up when the relays are off. This technique was used to accomplish the switching in some Boogie amps: the Mark IIAs, etc., and the "Rhythm 2" channel of Mark IIIs.

Cheers,

Gil

[heisthl]

What I don't like about that arrangement is that the LEDs are on when the relays are on, and they are in series, so whatever voltage drop there is across the LEDs will be subtracted from the power supply, so you might have some ringing problems with the relay coils.
Gil

I want the light when I turn the switch on - I've been doing it this way on all builds for a while now and haven't had any complaints or problems, but I use a 15v supply and 12v relays. The 12v relay is the most forgiving relay made, I think the specs on the ones I use say something like 7.5 - 17v range for turn on voltage. The Radio Shack transformer could be regulated at 15v if needed but I bet the relays will work fine (no chattering) even when regulated at 12. The footswitch LED's voltage drop are not cumulative (in theory) so worse case you should still have over 9v to run each relay.

[HiGain]

Thanks for the enlightening discussion above.

I'm still confused about my drawing with the series resistor and LED...

Looking at the diagram, the switches on the left are panel switches on the chassis, and the ones on the right are foot switches.

It seems like all the foot switches would do is turn on the LED (provided the panel switch is on), without switching the relay.

So, question... Are the footswitches supposed to be DPDT switches, with one pole operating the LED and the other pole shorting the (-) relay terminal to ground?

According to HAD, is the LED supposed to be ON in OD mode and in PAB mode? If the LED should be OFF in those modes, then couldn't I just put ground in the center lug of the foot switch, with the LED circuit being on one side of the throw and the (-) side of the relay coil being on the other side?

Again, still trying to understand this stuff...

Thanks

[ayan]

I want the light when I turn the switch on - I've been doing it this way on all builds for a while now and haven't had any complaints or problems, but I use a 15v supply and 12v relays. The 12v relay is the most forgiving relay made.

I hear you on the "LED on when relay on thing," that's why to me it was funny that Boogie called their scheme "Red = Rhythm" when I think all of us would expect the LED to turn on when the sound got "hotter." I have no experience doing things your way, I am sure you are right about the 12V relays being forgiving.

Cheers,

Gil