6
votes
Accepted
DIAC datasheet's circuit is not in series with TRIAC's Gate
That's not a "diac", it's a photo triac.
The gate-MT1 resistor is to deal with leakage and bias current in the photo triac and/or zero crossing circuit. It effectively lowers the sensitivity ...
6
votes
What is the importance of R1 connected in this circuit?
If \$R_{1} = 0\ \Omega \$, and \$V\!R_{1}\$ is adjusted to \$0\ \Omega \$, then the current through the DIAC and the gate of the TRIAC would be too high, causing one or both to be destroyed.
- 17.1k
5
votes
What is the importance of R1 connected in this circuit?
R1 limits the maximum current into the TRIAC gate when VR1 is at 0 Ω.
Because it is only about 1% of VR, it has very little effect on the brightness adjustment range.
- 23.2k
4
votes
one-way AC power
Here are some thoughts.
As Pieter said in his answer, this would be easy for DC: you would use a diode to prevent current to flow back to the grid.
But for AC, you can design something that behaves ...
- 1,765
4
votes
Zero crossing detection and Light dimmer
To make a light dimmer you have to use a non-zero crossing triac driver. For example, the MOC3051/52. These are sometimes called "Random Phase Triac Drivers".
You typically also need a zero crossing ...
4
votes
What is the importance of R1 connected in this circuit?
R1 gives you finer control.
Suppose the ideal range of total resistance is 900-1k ohms. You can get that control with a single 1k variable resistor, but you only would use 10% of the pots possible ...
- 4,668
3
votes
Accepted
Two or more Diac Triac dimmers in parallel
Parallel connection of 2-wire dimmer switches is fine.
Note that the first one to switch on will control the brightness. i.e., The one with the brightest setting will win. This is due to the way the ...
- 180k
3
votes
Zero crossing detection and Light dimmer
Devices such as the MOC3041 will only turn on as the supply goes through zero - this is desirable for controlling loads such as heaters or motors as it can reduce the interference they cause and avoid ...
- 34.2k
3
votes
one-way AC power
Disclaimer: I am just an amateur, get professional advice.
If you have two DC sources it would be easy, you just add a one way (diode) and power/current can only flow in one direction.
You might be ...
- 131
3
votes
How do DIACs work?
You can certainly use a transistor and trigger a triac (or SCR). Typically that takes tens of mA or more at a couple of volts. So a -5V supply and a resistor switched by a BJT works nicely for triacs, ...
3
votes
Accepted
Why are R1 and C4 connected in parallel to output in the following dimmer circuit?
R1 & C4 act as a snubber. They help to reduce voltage spikes due to the sudden change in current caused by the triac when it is switched on or off in conjunction with the inductance of the wiring.
- 11.2k
2
votes
Accepted
Triac control circuit through load
Why is it that in every triac analog dimming circuit I find that the triac triggering circuit is fed through the load and not straight from the mains?
In most countries there is no neutral available ...
- 180k
2
votes
Questions regarding eliminating hysteresis in ac dimmer
The root cause of the hysteresis (aka "snap-on" effect) in simple triac/diac dimmers is the capacitor not being discharged by the diac in the previous half-cycle and entering the subsequent half-cycle ...
2
votes
Accepted
A question on thyristors and phase control
Here is few factors come together. Flickering frequency is 120 or 100 Hz. Human eye can see it only by side view, not when you look straight. Second, voltage changes, but current amplitude doesn't ...
- 1,819
2
votes
Accepted
Simple DIAC circuit which I do not understand - LTspice
The DIAC will never reach a current that causes it to properly "flip". As voltage rises across the capacitor, the DIAC progressively steals more current away from the capacitor and you end up with a ...
- 473k
2
votes
TRIAC Voltage Control
Your schematic is wrong (missing a wire).
The wiper on the pot should be connected to the "bottom" end of the element. Otherwise there is no way for the diac to conduct sufficient current to ...
1
vote
TRIAC not triggering in 3rd quadrant but works perfectly in 1st
Try increase the LED current (and maybe pulse length if it is marginal). The MOC3020 is the least sensitive triac driver of that series and can take as much as 30mA to trigger (15mA typical at room ...
1
vote
Accepted
TRIAC BT136 as DIAC BD3 conversion both have MT1 and MT2
Diac and Triac work in different operating principles.
DIAC (diode for alternating current) is a diode that conducts
electrical current only after its breakover voltage. TRIAC
(triode for alternating ...
- 3,881
1
vote
Light dimmer not working
Online circuits aren't always good circuits to start with, they are sometimes tuned to the exact parts that were used without an analysis that proves that the circuit will work with normal part ...
- 17.4k
1
vote
How is Gate Trigger Current determined in a "dimming" circuit?
The Diac is a highly non-linear device. Below the diac breakover voltage, minimal current flows. When the breakover is reached, the diac conducts strongly and discharges C2 through the Triac gate.
The ...
- 17.4k
1
vote
This Potentiometer Keeps Catching Fire And I Can't Locate The Short
Obviously, too much current is flowing through the series R42/VR9 devices. A quick and dirty fix: if the VR9 pump control setting does not need to be at minimum rotation (0 Ω), and if the rework ...
- 5,241
1
vote
How do DIACs work?
Triacs (and SCRs) only need a about 1.2V to trigger, so, yes, a 5V circuit could trigger one.
Diacs have a kind of "snap action" when the threshold voltage is reached their voltage drop reduces to ...
- 36.4k
1
vote
Capacitor in parallel with relay coil backfires on contacts
If you happen to apply the power at the positive or negative peak of the mains (325 volts), for an instant more than 300V appears across R2||R3. Your series resistor R1 should probably be in series ...
1
vote
High(er) current AC flasher circuit
The circuit you linked to is for low power use. The 10uF capacitor provides little energy. All the current for the load (the led) goes through the diac, which has limited capability.
For higher ...
- 351
1
vote
110V sewing machine plugged into 220V - DIAC blew?
The component is almost certainly a metal oxide varister. It is designed to absorb voltage surges by shorting them out but it is not designed to take sustained overvoltage. Connecting a MOV chosen for ...
- 23.1k
1
vote
one-way AC power
Wrong kind of inverter. Get rid of it.
Take a close look at your solar panels. THEY ARE ALREADY DC. So just use actual diodes.
...
1
vote
one-way AC power
Here is my idea. Use a double conversion topology. It is the same approach used by premium UPS systems to isolate the load from the lines, except with multiple inputs.
For each line input, you would ...
- 11
1
vote
one-way AC power
It's going to be almost impossible without a deep knowledge of how that particular inverter detects the incoming mains supply. Block the mains, and the inverter will shut down, as it's designed to do....
- 20k
1
vote
one-way AC power
You got the wrong kind of inverter. A grid-tied inverter is never used for one specific load; you use it to convert the available power to grid power to supplement anything that might be connected to ...
- 178k
1
vote
Accepted
SCR triggering using DIAC
You are almost there.
The only missing thing is synchronization with ac votage. This is how you can achieve it:
Now the capacitor charging will be in sync with applied ac voltage. This will give you ...
- 8,511
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