can't test the voltage on DC appliance

[davelx]

Hmm, well, it worked for about 15 seconds by which time the heat generated by the contact arcing melted the solder!! So I couldn't get a look at the waveform. Unfortunately I only had a low current relay with NC/NO contacts, it might work better with an automotive relay.

Shame, as I was interested in what value of capacitor would tune the circuit for the best waveform.

 

[JohnW2]

Hmm, well, it worked for about 15 seconds by which time the heat generated by the contact arcing melted the solder!! So I couldn't get a look at the waveform. Unfortunately I only had a low current relay with NC/NO contacts, it might work better with an automotive relay.

It sounds as if you might have been running at an excessive current - how about trying some 'current limiting'?

Shame, as I was interested in what value of capacitor would tune the circuit for the best waveform.

I suspect that it would have to be pretty large to make the waveform even half-decent!

Kind Regards, John

 

[davelx]

It sounds as if you might have been running at an excessive current - how about trying some 'current limiting'?
I suspect that it would have to be pretty large to make the waveform even half-decent!

Kind Regards, John

I think it would need to form a resonant circuit with the transformer coil at the frequency that the interrupter was working at (which wasn't far off 50Hz, from the pitch of the buzzing).

You need the current to create the magnetic flux in the transformer - so reducing it would reduce the output too much, I think.

 

[JohnW2]

I think it would need to form a resonant circuit with the transformer coil at the frequency that the interrupter was working at (which wasn't far off 50Hz, from the pitch of the buzzing).

Yes, maybe ... as I said, a pretty large capacitor!

Kind Regards, John

 

[SUNRAY]

I think it would need to form a resonant circuit with the transformer coil at the frequency that the interrupter was working at (which wasn't far off 50Hz, from the pitch of the buzzing).

You need the current to create the magnetic flux in the transformer - so reducing it would reduce the output too much, I think.

The biggest issue with this is to stop the arcing with a spark quench circuit and very careful selection of component values will tune the frequency to 50ishHz however it is exceptionally unstable.
To improve the abysmal waveform the best place for adding capacitance is directly across the 230V o/p.

I tried this system some 50ish years ago with 3000 type relays with 15A contacts and took the abortion into school to test on their test kit, additionally I tried a 12-0-12 transformer to give a full wave o/p which did make a significant improvement to the waveform.

I ended up with a simple astable (OC71's) driving pairs of darlington pairs (OC71/OC23) via capacitors to improve the drive waveform feeding into a pair of 6.3V windings to power a 30W valve amplifier. I never did manage something stable enough to run a record player or taperecorder. but by then we had started using cassettes.

My grateful thanks to my physics teacher Mr Smith for the many hours he spent with me after school.

 

[JohnW2]

You need the current to create the magnetic flux in the transformer - so reducing it would reduce the output too much, I think.

Sure, but I suppose that the trick would be to try to find a 'happy medium', if one exists. As Sunray has said, suppressing the arcing would seem to be a high priority.

Since we are now talking 'electro-magnetic/electro-mechanical devices' maybe you should consider a motor/generator combination (i.e. a 'rotary converter')!

Kind Regards, John

 

[SUNRAY]

If I'm honest my original experiments using vibrating relays were not awe inspiring but I did have, what I consider to be, better results than the video.

Having viewed it again I can see why and I'm a little surprised no one else has noticed (apologies if you have and I've missed it) the transformer winding is in series with the relay so I'm not at all surprised the capacitor made a difference to the led lamp.

 

[davelx]

Ah. motor-generators, or dynamotors for DC output That brings back memories:

 

[SUNRAY]

Ah. motor-generators, or dynamotors for DC output That brings back memories:

View attachment 177308

I had 2 PSU's, one had a single Dynamotor and the other had a second which only started up on TX. Sadly set had been really badly butchered by the series of previous owners and the 'A' set PA (valveholder and all associated components) were missing. The 'B' set was completely missing and I butchered that area even more by cutting a hole in the chassis to take a mains transformer and built in a mains PSU.
Did you do the popular SSB mod?