SSVR's have built in trigger circuitry that turns the triac on for part of each 1/2 cycle of the AC waveform. A variable resistor (potentiometer) determines at what point in each 1/2 cycle the triac gets fired. Fire earlier for more power, and later for less power. The triac shuts itself off at the zero crossing at the end of each 1/2 cycle. So varying the potentiometer adjusts the pulse width of a pulse width modulated system.
Brew on
SSVR's have built in trigger circuitry that turns the triac on for part of each 1/2 cycle of the AC waveform. A variable resistor (potentiometer) determines at what point in each 1/2 cycle the triac gets fired. Fire earlier for more power, and later for less power. The triac shuts itself off at the zero crossing at the end of each 1/2 cycle. So varying the potentiometer adjusts the pulse width of a pulse width modulated system.
So if the potentiometer was disconnected from relay what would relay do?
I believe you would get no output without the potentiometer.
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Can you wire an SSVR in parallel on the element side with a standard binary SSR for such control? This way you could control boil either by PID/manual % or via knob control. Any implications to powering one while the other is off or on reduced output PW?
-BD
Sorry for a hijack from an electrical noob, but how does a SCR (silicon controlled rectifier) fit into this discussion? Any problems with using one to control a heating element that we should worry about?
This tells me there's a lot more than I thought that I don't understand. Are you saying that one of these will only give me half power to the element even when turned all the way up? If that is the case, could I use an element at twice the wattage and still get the heating power I'm looking for?You'd want a triac as they are bidirectional.
Since SCR's are one-directional, you'd already be at half power using one unless you full-wave rectified the AC coming into it first, which would require a full bridge (4 diodes).
This tells me there's a lot more than I thought that I don't understand. Are you saying that one of these will only give me half power to the element even when turned all the way up? If that is the case, could I use an element at twice the wattage and still get the heating power I'm looking for?
I know there are better options. I'm just trying to figure out how these things work.
No such thing as too much information, just the ability to comprehend it. Does this mean that the diode bridge will allow full power passed through to the element?From the Too Much Info dept: If it actually has an SCR inside, it must have a diode bridge to full-wave rectify before the SCR.
That looks like it will work fine. Sorry for being confusing, I had my engineering cap on.
(From the Too Much Info dept: If it actually has an SCR inside, it must have a diode bridge to full-wave rectify before the SCR. Or, it actually has DIACs / TRIAC inside)
Can you wire an SSVR in parallel on the element side with a standard binary SSR for such control? This way you could control boil either by PID/manual % or via knob control. Any implications to powering one while the other is off or on reduced output PW?
-BD
No such thing as too much information, just the ability to comprehend it. Does this mean that the diode bridge will allow full power passed through to the element?
So if the potentiometer was disconnected from relay what would relay do?
^^ bingo. It's essentially a PWM with a sinusoidal envelope. See the first graph below.
Hijack:
I'm planning on using an SSVR with PID (pot wired inbetween). When using the PID function I'll have the knob all the way up. When using the knob I'll just kick the PID over to manual mode so it's always on.
Any issues there? Probably should have researched it more before buying. But I don't see any trouble with it. I think I've seen it done that way before...
Hijack:
I'm planning on using an SSVR with PID (pot wired inbetween). When using the PID function I'll have the knob all the way up. When using the knob I'll just kick the PID over to manual mode so it's always on.
Any issues there? Probably should have researched it more before buying. But I don't see any trouble with it. I think I've seen it done that way before...
Yeah on my last two builds I've just used the PID buttons, but figured I'd bling this one out with a knob for boil control. Pointless maybe, but whatever.
Why not a separate socket for the HLT and BK?
Hijack:
I'm planning on using an SSVR with PID (pot wired inbetween). When using the PID function I'll have the knob all the way up. When using the knob I'll just kick the PID over to manual mode so it's always on.
Any issues there? Probably should have researched it more before buying. But I don't see any trouble with it. I think I've seen it done that way before...
I don't think hooking up a PID to an SSVR is a good idea. The voltages on the SSVR control potentiometer are not compatible with the PID voltages. Best case: only thing you destroy is your PID (unless it has overvoltage protection on its SSR control outputs.)
Brew on
I ran the PID to control one hot leg of the 240VAC and the SSVR with potentiometer to control the other. Works just fine, brewed about 10 batches with it so far. The PID I had was the TA4 so it couldn't do manual duty cycles. It is somewhat unnecessary with a TD4 or comparable PID. The knob is quicker to adjust though. A bunch of button presses on the PID can be frustrating if you're in panic mode to prevent a boilover. I found that keeping a metal pan close at hand and scooping a pan-full of wort will be enough of a heat sink to stop the boilover in most cases
Yeah you guys are right. I can't control the SSVR with PID's 12v output. Should have caught that. I'll have to think about this some more. Feck. Don't want to do 2x relays. Probably just scrap it and do the buttons afterall...
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