I tryed different comparators and I saw they work the same. I didn't used ICs because I didn't find one digipot with parallel comunications, wich carries us again to serial, and it would be more circuitry. So, the AD drives the potentiometer, who is the RC circuit of timing for phase control.
#LOGICWORKS RC CIRCUIT MANUAL#
This resistance is in series with a manual potentiometer, with wich I define a minimum, that is, the minimum velocity of the motor, supposing that as higher it be, longer the time to light up the triac. As the voltage in the input grows up, the resistance will be less, in 7 steps.
The bc547 bridges a series or resistors, depending on wich is on, should give a correspondant sum of resistors. I'm trying to put this three concepts together: Thank you in advice for your comments and have a good week. In another item, If someone have the 6N136 spice model, I would appreciate it very much if it is shared. motor? (Or happily maybe someone has the spice model to be added to proteus 8)ĭo you think it would be better to make a frequency oriented circuit? (Please don't say it is "difficult" because this word can be bad lucky. I couldn't simulate the power stage as proteus doesn't have a monofasic AC motor model, Do you know how with a capacitor and a resistance could I simulate the effect of the 1 h.p. I added too an optocoupler but I'm not shure it works fine with this circuit.ĭo you think it is O.K. That would be the fine control, together a base level (a manual potentiometer preset) wich in conjunction with a capacitor, they make the RC timing of phase control. (you can see it in simulation, so as the control input oscilates the right leds get on) The resistors in the input are thought for a 5 V range, and the output are 0K to about 50 K, but somebody could change that to meet his needs.
In order to have some control I added an 8 bit AD coupled with a digital potentiometer made with discrete components. induction motor to be operated only over 70% of its capacity. So I did a circuit oriented to phase control, as you recommend me, thinking in an AC 1 h.p. Obviously that means you have no real control over the power you allow to reach the motor, the triac will fire almost randomly and always remain conducting until the next zero crossing point. As you have no synchronism between your own 60Hz oscillator and the line frequency, the pulse, no matter how wide it is, could turn the triac on at any time in the AC line cycle. The reason it wont work is the pulse width, within reason, is irrelevant, even a very short pulse will turn it on, it is the time into the AC cycle that matters. What you are trying to achieve is control of how much of each AC line cycle is fed to the motor and your circuit attempts to do that by using different pulse widths to trigger the triac. If you trigger the triac at any time while there is voltage across it, the conduction will continue until the next zero crossing of the current (when it equals zero). The current will also be passing through zero twice per cycle although slightly out of time with the voltage because of the inductive nature of the motor. As the circuit is working on AC, the voltage will be reversing in polarity, half a cycle in one polarity then the other half in the reversed polarity - which by implication means it passes through zero twice on each cycle. The complication is that it doesn't turn off when you remove the pulse, it keeps conducting until the current passing through it is externally removed. It is probably easiest to image it is a triggerable switch, when you fire a pulse at it, the switch turns on. It isn't a controlled resistance as you originally quoted and it isn't an 'on or off' switch in the conventional sense. Expanding what was said in posts #11 and #12, you have to understand how a triac works.
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