General concept for selecting the bleed resistor.

1) Setup a test with the 10W lamp wherein it is connected to the 240VAC then to LAMP then to 1 ohm 10W resistor then to SSR and then to the AC return. See figure below:



2) Arrange the SSR inputs in a manner to keep the SSR in the OFF state. (This may be simply leaving then open).

3) Setup the Oscilloscope in the A+Binverted DC coupled mode and probe A and B channels across the 1 ohm resistor. The display should allow you to read out a voltage that corresponds to the leakage in the OFF state SSR. Note that this scope reading will fluctuate if the lamp enters its oscillatory mode. Make sure to the reading when the lamp is in the OFF state. Convert the reading from the scope to an RMS value. Lets call this voltage V1.

4) Compute a bleed resistor value such that the current that it can shunt is about 5 times the current value that corresponds to the reading taken in step 3 when the shunt resistor has 240 VAC RMS across it. The following formula can be helpful:

            V1           5 * 240
           -----    =   ----------
             1             RBLEED

5) Test the bleed resistor in the real circuit across the SSR terminals. Use care to compute the wattage needed for this selected resistor value and then allow for a good 2::1 design margin and select the appropriate resistor rating.

Michael Karas