Put together this schematic just now. I'm planning to use one of the triacs for phase angle control while the other will be used as a solid state relay. I have a zero crossing detector somwhere else in the schematic. just wondering if this is a good solution. The microcontroller will be a esp32.
I don't think 1k is realistic for the current-limiting resistor on the opto inputs... Try 220 ohms giving
about 15mA which should be enough for any opto-isolated device to operate reliably.
MarkT:
I don't think 1k is realistic for the current-limiting resistor on the opto inputs... Try 220 ohms giving
about 15mA which should be enough for any opto-isolated device to operate reliably.
Done. thank you for the advice!
RippoZero:
If your load is inductive, look at the examples (Fig.12 and 13) in the MOC3021M datasheet
Not sure why you have two optos and two triacs when you could:
Diagram:
Yours,
TonyWilk
yeah i looked at the datasheet and followed the example. The idea with the second triac is that i want some redundancy cause if my machine does not turn off when it needs to my house might explode.
Is pwm usable to switch AC? I thought that would make crazy noise.
RippoZero:
The idea with the second triac is that i want some redundancy cause if my machine does not turn off when it needs to my house might explode.
Ok, I suppose two triacs might cover for the case when one of them blows up and goes short-circuit.
However, if you have both of them controlled from the same esp32 it's more likely that something in the software fails to turn off the triacs.
If you have some independent 'fail-safe' circuit handling the ON/OFF, you can use that in my cct. above - or stick with your two triac solution of course.
Is pwm usable to switch AC?
Sorry, I should've labelled that Phase Angle Control, not PWM.
Yours,
TonyWilk
RippoZero:
The idea with the second triac is that i want some redundancy cause if my machine does not turn off when it needs to my house might explode.
That counts as a safety critical device, which has obvious legal ramifications. For instance the Atmel disclaimer
on their microcontrollers etc:
- SAFETY-CRITICAL, MILITARY AND AUTOMOTIVE APPLICATIONS
(a) Products are not designed for and will not be used in connection with any applications where the failure of such Products would reasonably be expected to result in significant personal injury or death ("Safety-Critical Applications") without an Atmel officer's specific written consent. Safety-Critical Applications include, without limitation, life support devices and systems, equipment or systems for the operation of nuclear facilities and weapons systems. Buyer will fully defend (at Atmel's option), indemnify and hold Atmel harmless from and against any cost, loss, liability, or expense arising out of or related to use of Products in Safety-Critical Applications.
(b) Products are neither designed nor intended for use in military or aerospace applications or environments unless specifically designated by Atmel as military-grade. Buyer acknowledges that any such use of Products not designated as military-grade is solely at Buyer's risk, and that Buyer is solely responsible for compliance with all legal and regulatory requirements in connection with such use.
(c) Products are neither designed nor intended for use in automotive applications unless specifically designated by Atmel as automotive-grade. Buyer acknowledges that any such use of Products not designated as automotive-grade is solely at Buyer's risk, and that Buyer is solely responsible for compliance with all requirements in connection with such use.
So where exactly is the load ? (I see one or two snubbers, but no load)
I see and ac source and a semiconductor switch (one or both traces), but no LOAD.
WHERE is the LOAD ?
The load is going to be a stepper motor run with two h-bridges and a heating element
Why is it not shown in the schematic ?
Stepper Motors ? (AC ?)
How does that work ?
Can you tell us what would happen if anyone built the circuit you posted and turned on the triacs ? (think about it. How much resistance do you think there is in the circuit path with no load? What will happen to the triacs (and the wire) with nothing to oppose the current?
I suppose two triacs might cover for the case when one of them blows up and goes short-circuit.
If one of them blows up it becomes an open , and the load will turn off.
If one of them shorts , a second one could open up the circuit.
It sounds like you should consider a fail-safe circuit to detect open/close status of the trial.
probably should have answered you better earlier. the main load is a resistive heating element drawing at max 20A at 230 volt. In adition to that there is a 12V switched PSU supplying a stepper and some other motors. to supply the microcontroller i use a buck converter. the triacs will be switching only the resistive heating element as the rest need not be turned off during normal operation.
ALSO this is where i'm at now.
Still no heating element in the schematic
(that I could see)
1/ There is no point in using two triacs in series.
2/ In your circuits if you turn both on they'll short across the mains and blow up.
3/ You can't drive stepper motors with ac like this - and your H-bridge will blow up too. It needs a dc supply.
Any more?
Allan.
1/ There is no point in using two triacs in series.
2/ In your circuits if you turn both on they'll short across the mains and blow up.
3/ You can't drive stepper motors with ac like this - and your H-bridge will blow up too. It needs a dc supply.
Yes, Allan, I have been trying to tell him the same thing.
He says the ac load is a 240vac heating element, which for reasons unkown he continues to omit from his schematic. i tried to tell him that he shouldn't post a bad schematic like that that has no load because other less experienced members might see it and think that because someone posted it that it must work.
That's better but you might want to consider a circuit breaker or fuse in series as well.
Yeah i got to fuses in the main schematic. Cut it down to make it easier for you guys.
Yeah i got to fuses in the main schematic. Cut it down to make it easier for you guys.
FYI,
"to" is spelled TWO if you mean the number...
just sayin'...