sweet. this is more along the lines of what i was thinking, i just hadn't heard nor seen of it.
anybody on here done this before, or have any links of examples on how to get a set up like that going? i will still probably build a box of some sort, to house the "dimmer switch" knob and ssr, and the two female 220v plugs for the two heating elements, and a "kill all" switch, and then a three way switch set up for hlt element on, all off, bk element on.
Yeah, you still need a control box. I just meant that it didn't have to be a fancy one.
I've built a couple of the pulse width modulators in the past few weeks. Here's a short (and modified) write up with a video I put in another thread recently:
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Exmaple PWM schematic:
The two components in blue (larger capacitor and the potentiometer) are where you can make changes to control the frequency of this thing.
The frequency will be:
1.44/(C * R)
So, in this example, the circuit will have a frequency of
1.44/(0.000020 * 100000) = 0.72Hz
It will go through one timing cycle every 1.38 seconds.
You can use different sized potentiometer and/or capacitor if you want your cycling period to be longer than this. I actually used 33uF caps on mine for a lower frequency of 0.43Hz (one cycle every 2.3 seconds).
By turning the knob on the potentiometer, you can adjust how much time out of that 1.38 seconds the pulse will be ON vs OFF. Turn the knob all the way one direction and the element will basically be on 100% of the time. Turn the knob all the way the other direction and the element will basically be on 0% of the time.
You will need to supply the circuit with a DC voltage source. If you have an old cell phone charger or other old power adapter lying around, you can use that for the DC source.
The end result is that the "dis" (discharge) pin of the 555 timer chip will periodically drain current (as controlled by your knob setting). When the discharge pin is sinking current, you will get a voltage difference between the + and - wires that are marked as "relay control voltage", and the relay will allow your 220V to pass through. When the discharge pin is not sinking current, there will be no voltage drop across the relay control and the relay will not allow the voltage through.
Here's a video of mine packaged up in a small box:
I don't have any pics of the inside of that box, but I can take some if you want to see it. All that's in there is the guys of an old cell phone charger I had in a drawer (I took the plastic case off so that I could slide it into the plastic box) and a small circuit board with the PWM components on it.
The schematic does not show it, but I added a small LED and 1kOhm resistor so that I could get a visual of the duty cycle easily. That part is not necessary, but blinking lights give it a nice geeky factor.
I plan to cut a rough hole in the front of my control box for the potentiometer and LED to be able to pass through and then drill a couple holes so that the face plate of that thing can be put on the front of the control box and the rest of it can sit on the inside of the box.