Hello!

So I have always been interested in power electronics, purely as a hobby. I have little interest in the whole digital/microcontroller stuff, in fact I prefer to not use semiconductors whatsoever. I suppose other than the odd bridge rectifier.
Recently I have been on the rediscovering arc again, and been tinkering with purely electromagnetic relays and solenoids after being inspired by an old arcade machine.
I want to run it all on DC power, as battery power is quite handy, and so is solar.

I have managed to make some test coils to play around with, and so far I have learned that the solenoid works wonderfully, but I have trouble figuring out how to manage the power it gets. My current idea is to use some capacitors, that save up energy, to then give a good sudden whack. Then there would be a couple seconds time before needing for it to fire again.
So I assume the higher the voltage, the higher power I can deliver to the solenoid. So if I have a relatively high voltage capacitor, say 25 or 50 V. Probably have a line of Farad caps for buffering, that then feed a surge cap that unloads into the solenoid. Is there even a non semiconductor way to charge a higher voltage cap from a lower voltage source, like a 12V battery?

How can I limit things, so that the solenoid doesn't actually fire until a voltage threshold is reached?

I thought maybe I could wind a relay, and set it up so that it only closes contacts when a certain threshold is reached, but I'm kinda at a similar problem there, how do I change that trigger voltage? Bunch of resistors maybe?

I suppose I welcome any pointers really. Just tinkering about with coils I wind.

 

Is there even a non semiconductor way to charge a higher voltage cap from a lower voltage source, like a 12V battery?

Yes, pre-transistor car radios used an electromechanical buzzer to drive a transformer to get the high voltage needed for vacuum tubes.

 

Here's the simple schematic of a typical tube car radio circuit that used a mechanical "vibrator" to generate the square-wave AC voltage that is then stepped up by a transformer to a higher voltage.
The battery voltage connects to the + node.

Below that is the picture of a typical vibrator.
It was removable since the contacts had a limited lifetime, and had to be periodically replaced.

 

There was also a synchronous vibrator version that switched both primary and secondary so that no rectifier was required!

 

Correct, you need a synchronous vibrator for DC output.

 

Here's the simple schematic of a typical tube car radio circuit that used a mechanical "vibrator" to generate the square-wave AC voltage that is then stepped up by a transformer to a higher voltage.
The battery voltage connects to the + node.

Below that is the picture of a typical vibrator.
It was removable since the contacts had a limited lifetime, and had to be replaced.

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View attachment 358675

I am using DC power though, does this only work with AC?

 

Correct, you need a synchronous vibrator for DC output.

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That is quite advanced to what I usually do I am intrigued however! Can't wait to tell people I build a vibrator.

 

That is quite advanced to what I usually do I am intrigued however! Can't wait to tell people I build a vibrator.

Just wait until you explore multi-vibrators.


There are limits on what can be done purely electro-mechanically with a few passive components but knowing those limits requires just a little addition knowledge.

 

Just wait until you explore multi-vibrators.
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I will need some time to understand what and how it's doing.

 

I am using DC power though, does this only work with AC?

The input power is DC.
The vibrator converts it to AC for the transformer to work its magic.

 

I will need some time to understand what and how it's doing.

I doubt your girlfriend would be impressed. Solid-state oscillators can do the same job as the relay if you're interested?

 

I doubt your girlfriend would be impressed. Solid-state oscillators can do the same job as the relay if you're interested?

But she told me not to worry about it!
In truth I have no idea what oscillators do but I'll have a read.

 

Correct, you need a synchronous vibrator for DC output.

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PS reading about it, I really like the idea of building one of these. Are you available somewhere, sometime for a chat?

 

PS reading about it, I really like the idea of building one of these. Are you available somewhere, sometime for a chat?

No.

 

Oscillators swing voltage up and down in a repeating pattern. In the case of the vibrator the voltage goes to the full 12 Volt line and then to the ground which is the negative lead. Transformers can pass an AC signal through them with power. And so boost the voltage of the up and down movement, AKA AC (alternating current). which is what your wall outlets provides.

 

......And if you switch the output of the secondary in sync with the primary, the result is DC without a rectifier device. per-se. !
As per #4 & #5.

 

I suggest that prior to constructing such systems, that the TS investigate the efficiency of these schemes. The knowledge gained will probably be useful.

 

transformers are things that allow you to step up (or step down) voltage. but they only work with AC.
that requires some way to create oscillations. a simple relay can be abused for such purpose just wire coil and one of NC contacts in series, and connect it to a battery. it will chatter away and you will see sparks.
next you can connect it to a small transformer. this way transformer will get DC pulses instead of AC but one way to look at them is as a sum of steady DC and AC. as stated before transformer does not care about DC but the AC part will do. depending which side of transformer is connected to a relay you can higher or lower or same output. if you like higher, then connect low voltage side of transformer to the oscillator.
that is two milestones already but you get AC output. to charge battery you need DC.
without using diodes, you can apply learned and use another set of contacts from that relay to switch the output side (higher voltage AC), since this works at same pace as relay oscillator, this extra contact will only connect to transformer on one half-period. in other words you got yourself a synchronous rectification without going back in time or robing museums.