Triac testing

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DIYspanner

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The triac sits in the pcb control board of a Bosch Classicx 1400 washing machine. The image I've attached is merely to show the terminals, the part no for mine is BTB16 600CW.

I've watched a number of videos on YT about testing them but its confusing.

With the multimeter set to Ω, there should be a reading between and MT1 and G terminals.

Between MT1 and MT2 there should be open circuit until MT2 and G are bridged but to my mind that's only allowing MT1 and G to make circuit and doesn't confirm that MT1 and MT2 are connecting to make circuit.

Can anyone clarify for me please?

full
 
DIYspanner said:
I've watched a number of videos on YT about testing them but its confusing.

With the multimeter set to Ω, there should be a reading between and MT1 and G terminals.
Click to expand...

The only way to test them, is functional testing. Basically you watch for the trigger on the gate, and see if when the signal is there, that the triac switches on.
 
This has me intrigued.

According to this webpage, using a multimeter, MT1 and MT2 should remain connected after the connection to Gate is removed. With the test I've done, removing the link between MT2 and Gate causes MT1 and MT2 to open circuit from each other.
 
DIYspanner said:
This has me intrigued.

According to this webpage, using a multimeter, MT1 and MT2 should remain connected after the connection to Gate is removed. With the test I've done, removing the link between MT2 and Gate causes MT1 and MT2 to open circuit from each other.
Click to expand...

MT1 should remain connected to MT2, once triggered, until the voltage across them falls Ito zero/crosses the zero line/goes negative. It will then remain off, until retriggered by a voltage on the gate.
 
To be precise..... After being triggered to be ON the Triac will continue to conduct MT1 <-> MT2 until the current MT1<->MT falls to be less than the holding current for the device at which point the Triac will switch OFF.
 
bernardgreen said:
To be precise..... After being triggered to be ON the Triac will continue to conduct MT1 <-> MT2 until the current MT1<->MT falls to be less than the holding current for the device at which point the Triac will switch OFF.
Click to expand...

Correct, but I was trying to keep it simple....

Once it 'drops out', it remains 'dropped out', until retriggered. To form a dimmer triac, the retriggering, is delayed, to a point determined by the control, on the rising (or falling) waveform. Thus, the lamp, or etc., gets a pulse of energy, of a time length, dependent on the setting of the control.

For a simple on, or off control, the triac has to be constantly retriggered, at every zero cross point, or just after.
 
My own definitive test!

12v battery and brake light bulb.
Battery + terminal to bulb base, bulb collar to MT1, MT2 to back to battery - terminal.
I bridged MT2 and Gate with tweezers, the bulb lit and stayed lit with tweezers removed.
A satisfactory test?

full
 
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