relay supply voltage

[paddes53]

Hi,

I just finished (yet another) ODS style amp running two 6v6 valves. Unfortunatley I've got some issues with my relay switching. Im using the standart voltage doubler off the 5V heater taps and into a 78s10 voltage regulator. When none of the coils are grounded the supply voltage sits at about 10V as it should. When switching only one relay in, the voltage drops to about 3.9V all of a sudden. So effectively I can only switch one relay at a time. My question is, do I need to bump up the voltages of the supply or (sigh, since I hardwired them) do I need to look at different relays since the current draw seems to be so high ?


Any help would be appreciated.

regards,
Patrick

[Funkalicousgroove]

You have something mis-wired somewhere, My supply sits right at 5v relays in or out.
What kind of relays are you using?
do you have a diode across the coil?
what kind of power supply setup do you have?

[paddes53]

ok, the relays are 6V finder 40.52 types which i bought from a local
electronics supplier. i took a look at the datasheet (http://www.finder.de/comuni/pdf/S40EN.pdf) but couldnt find any
info on the actual current draw.
As for now I don't have a diode across the relay coil, but I can't see how this would make a difference that large in voltages.
The power supply is just a standart voltage doubler off the 5v heater winding of the PT into a 78s10 voltage regulator with another filter cap at the end, all of the ps caps being 100uf/35V. All the ps grounds are connected to the chassis.
The only thing I can think of are the relays being fed a too high voltage but I didn't think that they were so picky about voltage.

[heisthl]

Hi,

When switching only one relay in, the voltage drops to about 3.9V all of a sudden.

Patrick

if your measuring 3.9v right at the regulator your relays are drawing too much. Get some different relays or try not using a doubler or a regulator.

[paddes53]

Would a simple bridge rectifier for this purpose ?
The lower voltage shouldnt be an issue since the relays are 6v
anyway, it should be enough to operate the switch.
What still puzzles me is that I used the same ps and relays on another build without these problems.

[Funkalicousgroove]

First off, your filter caps should be more like 1000 uf, sounds like the ones you have aren't storing enough energy.

Try NTE R40-11d2-5/6 relays, I use them and have seen them in a few Dumbles, they always work great.

[skyboltone]

Hi,

When switching only one relay in, the voltage drops to about 3.9V all of a sudden.

Patrick

if your measuring 3.9v right at the regulator your relays are drawing too much. Get some different relays or try not using a doubler or a regulator.

My experiments agree with Heisthl's conclusions. I am using an icecube relay from Mouser that draws 40ma. I've bridge rectified the 5 volt winding into a 1200mfd cap. With both relays energized the voltage is about 6.2 or three. With one working it's about 6.9. They work fine. Don't ground the supply.

[Funkalicousgroove]

I rectify FWB using a filament transformer@ 6.3v, then a 1000uf@35 then an NTE 6v regulator, then another 1000uf. I get 5.9-6.1 vdc (depending on the regulator) with or without the relays engaged. The negative side of the rectifier, the negative side of the caps and the center pin of the regulator are all grounded.

[skyboltone]

I rectify FWB using a filament transformer@ 6.3v, then a 1000uf@35 then an NTE 6v regulator, then another 1000uf. I get 5.9-6.1 vdc (depending on the regulator) with or without the relays engaged. The negative side of the rectifier, the negative side of the caps and the center pin of the regulator are all grounded.

I wonder if the fore and aft caps is what helps the regulator regulate. dunno.

[Funkalicousgroove]

I got the circuit straight out of an Overdrive special, I've always used it, so I have no Idea.

[skyboltone]

I got the circuit straight out of an Overdrive special, I've always used it, so I have no Idea.

I wonder if I bought the wrong regulator.

Anyway, back to the original post. Make sure you have DC coils if you're using DC supply. The AC coil relays will not run on DC. They are designed to be very inductive and have high impedence at 60hz.

[paddes53]

Yesterday I rewired the ps to a bridge rectifier with a 1000uf filtering cap. The relays switch ok, but the voltage still drops to about 4.3 when the 3 relays are on. Maybe I should try using a 5v regulator with another 1000uf ish cap at the end and see if the voltage remains constant. Anyway Im guessing I just used too large relays, the ones ive got are 8A 220V types.
Thing is the smaller relays are really a pain to wire point-to-point like i did with these

[Funkalicousgroove]

Use an IC socket and small turrets, it makes PTP much easier with relays.