What Capacitor to use in this half wave rectifier circuit to encode signal?

[spec]

As a mater of interest, what would you-all do if you wanted to control more than two relays via one wire?

spec

 

[Les Jones]

Hi spec,
If "C" is a smoothing capacitor it can't work when both switches are closed as there will be AC across it. An alternative to a capacitor across the relay coils would be a diode across them (For R1 the cathode to the bottom end of the coil.) The coils would probably have enough inductance to maintain the current via the added diode during the unpowered half cycle.

Les.

 

[silas greenback]

Thanks everyone for your help on this, you have to love the internet, I honestly don't know where else I could get this kind of information so easily, so thanks again

Dave

 

[spec]

Hi spec, If "C" is a smoothing capacitor it can't work when both switches are closed as there will be AC across it. An alternative to a capacitor across the relay coils would be a diode across them (For R1 the cathode to the bottom end of the coil.) The coils would probably have enough inductance to maintain the current via the added diode during the unpowered half cycle. Les.

Nice analysis Les,

So you spotted the obvious flaw in my circuit.

Back to the drawing board (note pad).

spec

 

[spec]

Thanks everyone for your help on this, you have to love the internet, I honestly don't know where else I could get this kind of information so easily, so thanks again

Dave

Good luck to you Dave.

Chuck

 

[ronsimpson]

Back to the drawing board

 

[Les Jones]

I have found some relays that have a coil rated at 240 V AC or DC This is the link to them at CPC
This is a link to the information on them. The coil rating is on page 121. I think two of these relays should do what you want.

Les.

 

[spec]

View attachment 101857

Nice schematic Ron, but why two 9K1 resistors? Or am I missing something?

I'm being pedantic again, but the diode PIV is not quite there (600V).

spec

**broken link removed**

 

[spec]

I have found some relays that have a coil rated at 240 V AC or DC This is the link to them at CPC
This is a link to the information on them. The coil rating is on page 121. I think two of these relays should do what you want. Les.

Well done Les. As usual, you have come up with the goods.

spec

 

[silas greenback]

Good luck to you Dave.

Chuck

Thanks Chuck

 

[silas greenback]

I have found some relays that have a coil rated at 240 V AC or DC This is the link to them at CPC
This is a link to the information on them. The coil rating is on page 121. I think two of these relays should do what you want.

Les.

Thanks Les!

 

[Les Jones]

I have had some more thoughts about this relay. I have never seen a relay before that is rated for both AC and DC so I was wondering if this is just a DC relay with a bridge rectifier built into it. Also calculating the value of a smoothing capacitor would not just calculating the value so it did not discharge much over half a cycle. The capacitor would charge to near the peak voltage of the mains supply. (240 x 1.414 = 340 volts) Some allowance would have to be made to the value to allow for this.

Les.

 

[ronsimpson]

(240 x 1.414 = 340 volts)

That is why I added a resistor so the circuit will not peak rectify.

but why two 9K1 resistors?

1) was not thinking.
2) twice as much heat in one resistor. (if two switches are closed)