VLS631 Thermal Delay

[Dagwood]

Hi

Has anyone here used one of these???
http://tubedata.tubes.se/sheets/061/s/S102-1G.pdf

I picked up a few a while ago and wondered how they operate the relay and then switch off, cant quite picture how a relay will hold the circuit closed with no coil current, other than latching....but then you have the issue of resetting the relay to switch off the circuit

I'm confussed!

 

[djQUAN]

It's like a thermostat. It closes when hot and opens when cold. The "coil" is a heater.

When current is applied through the heater, it takes a certain amount of time to heat up then close the contact hence the delay. When the current is turned off, It takes a certain amount of time to cool off before opening.

That's how I think it works

 

[Dagwood]

Hi djQUAN

Thanks, thats the bit that I do understand

I have mocked one up and it works fine, I just dont see how the relay works in the circuit??

Cheers

 

[Shoog]

I have used a similar thermal relay and my experience is that they latch off almost immediately you remove the current.

Shoog

 

[Dagwood]

Hi Shoog

I agree, the one I tried does exactly that, maybe a couple of seconds.

The datasheet advises to use a relay to switch "larger powers", how did you do that?

Cheers

 

[DigitalJunkie]

You would connect it more or less like a normal relay. The heater would take place of the coil,and you would use the switched contacts as usual,to control a larger load.

 

[Dagwood]

I think this is more like a thermal transistor, think of a transistor driving a relay, this replaces the transistor, the relay handles the larger load

 

[Shoog]

The one I used has a biometalic strip which switches the +B load of about 200mA at 350V. The tube I use is wired in series with the power supply (+B) and the drain resistor applies the initial heater current to switch it. Delay is about 10secs in this configuration. Maybe a slightly different type to the ones you have.

Shoog

 

[Dagwood]

Hi Snoog

The STC valve has a lot lower rating, 100ma @ 50V dc when contacts break.

Maybe a dual coil relay may work?

 

[Shoog]

I only tried using this because I had one salvaged.
Generally I use a very simple single transistor relay driver for my time delay which has worked flawlessly in all the configurations I have tried.

Shoog

 

[Dagwood]

Hi Snoog

Yeah I know these circuits are all over the web but I was just keen to get another piece of glowing glass into my projects

I just can't see how the relay will reset once triggered by the thermal switch??

Cheers

 

[TheGimp]

I had a tube similar to that which came out of a Tektronix Oscilloscope.

6N045T

I used it to switch B+ (300V) to a 6P1P PP amp for a while. It eventually failed, but I suspect it had a crack in the base.

It uses a bi-metalic thermal strip which works quite well.

 

[Shoog]

Hi Snoog

Yeah I know these circuits are all over the web but I was just keen to get another piece of glowing glass into my projects

I just can't see how the relay will reset once triggered by the thermal switch??

Cheers

Just as in the transistor circuit - the relay unlatches as soon as the mains power is disconnected.

Shoog

 

[Dagwood]

On the datasheet it says to use the NC contacts on the relay to disconnect the heater supply on the thermal switch once the bi-metalic thermal strip has connected as it should not be loaded long term.

Cheers

 

[rotaspec]

Hi Snoog

Yeah I know these circuits are all over the web but I was just keen to get another piece of glowing glass into my projects

I just can't see how the relay will reset once triggered by the thermal switch??

Cheers

I have some of these too. They use a bimetal strip that bends when heated due to applied current. They are quite slow in operation (not like the snap action of a relay) so they are not suitable for high HT voltages.
Also, the bimetal takes about 500mA of heater current to operate (and that is needed continuously) so they are a mixed blessing.

Gary

 

[Shoog]

I wouldn't bother again.

Shoog

 

[Dagwood]

Is there a relay that will hold using the load current once it is triggered?