using a Thyristor Module for heatbed?
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@jens55 not more than i can get them for free but i never used any so i dont know how they work
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@tazla, gotcha. 'Free' is a powerful motivator
My take on the situation as far as I understand it (not very far)- the standard SSR has isolation between the trigger circuit and the power circuit (4 terminals). A Thyristor is a three terminal device that would rely on the same ground between trigger and the power circuit.
I would not attempt to use this device. SSR's are proven to work perfectly.
In addition, I think a Thyristor can switch off current at any point in the AC wave cycle which in the application of a heated bed controller could generate all kinds of EMI. -
Given the generally low cost of applicable DC-AC SSR units I don't think it's worth it.
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@phaedrux ok then i use a ssr to be safe
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@tazla, good choice !
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@jens55 said in using a Thyristor Module for heatbed?:
In addition, I think a Thyristor can switch off current at any point in the AC wave cycle
IIRC it's the opposite way: they have a 'zero-crossing' detector to switch OFF at 0V, but depending on the PWM switch ON at any voltage.
Nevertheless, they might be an interesting option for 24V - 60V AC consumers. The PSU would be more economic. (no rectifier losses)
Just a minor point for most of us. -
I'm pretty sure that a Thyristor (unlike a Triac) will only conduct the voltage in one direction, so if this module really is just a Thyristor you will only get half of the AC waveform.
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@gloomyandy yes a thyristor conducts one way only. They can be used in conjunction with bridge rectifiers to control AC, but triacs have less voltage drop than this arrangement; so triacs are more commonly used when AC needs to be switched. For switching high current AC, a pair of back-to-back thyristors is another option.
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Right, I confused that. And I'm almost sure it's a Triac that has 'zero-crossing' detection.
I forgot that I have Alzheimers
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@o_lampe said in using a Thyristor Module for heatbed?:
Right, I confused that. And I'm almost sure it's a Triac that has 'zero-crossing' detection.
All triacs turn off at zero crossing. Most DC-AC SSRs have additional circuitry so that they only turn on just after the zero crossing too.
