Solid state relays tend to produce less noise & EMI vs. a mechanical relay, all else being equal. For one thing, mechanical relays will produce an arc across the contacts when they open and/or close, resulting in radiated and conducted noise. In addition, solid state relays smoothly transition when going from open to close, and close to open, resulting in less EMI in the high frequency range.
With some solid state relays, you can pay a little extra and get one with zero-crossing circuitry. This means that, when you tell it to energize, it will wait until it sees zero voltage, and then it will energize. This greatly reduces EMI and stress on the system.
Solid state relays have some disadvantages, of course. They can get pretty hot when energized and when carrying lots of current, so a heat sink is often necessary. And the “contacts” are never completely closed or completely open: when “closed,” the contact resistance will be greater vs. a mechanical relay, and when “open” the contact resistance will be less vs. a mechanical relay. When the solid state relay is deenergized, it should be kept in mind that there could still be a small voltage across the load, and a small current through the load.
The only part of any Amazon product link you need is https://www.amazon.com/dp/B08FR13GYR/
Everything else is search query or tracking crap. Find the 10 character alphanumeric code after the “/dp/” part, include that plus a trailing slash, and remove everything else.
I wanted to order one of these devices from the much-discussed Amazon link so I grabbed a spare machine and motor and ran it while plugged into a Kill-A-Watt to see power requirements.
That’s not the issue–the motor ran with 270mA and 18W… something is funny there since P=IE doesn’t seem to hold true, but it’s all pretty low so I’m not worried about blazing heat.
But as I ran the mechanism through its paces I remembered that because these machines use rollers rather than belts, they cannot be shut off while the capstan is in contact with a roller, lest you leave a divot in the roller for eternity.
There is a way to avoid this, and indeed the machine has all kinds of mechanical linkages that open and shut contacts in such a way that when you say “shut down” it stops the motor only after the capstan has disengaged, but that involves old pinball-machine-style leaf contacts opening and closing so I would still have the problem.
So what seemed to be a simple project suddenly became more complicated.
Considering how this is meant to be a reasonable imitation of reality, I am considering jerry-rigging some way to let the platters free-wheel and use a modern motor with a belt to drive them.
