dnex6lizrd
New Member
Hi, this is a solid state relay that ive been having trouble with lately. I think i get its operation, using a separate electrically isolated small signal circuit to control a large load.
Light flows from LED into phototransitor, making it conduct more through base branch. The increase of current base biases the first Q more making it conduct enough to turn on SCR. SCR shorts out the rest of DC circuit which behaves as a load resistance to AC circuit. Increased curren in AC fires traic which shorts the entire circuit leaving only source, light, triac, and transient suppressor RC. This AC current needs to keep bulb at full brightness when LED is on, and OFF when LED is off. Thing is that i cant get the values to do this. Also, when SCR is off, current flows through both transistor and phototransistor. Can you help me understand how to keep flow from just under firing SCR, and doing so when LED is on. AC resistor values must also play a role. Id appreciate it.
*please note that the negative of bridge rectifier is not supposed to connect to the ground of ac, its supposed to be ground of the dc, there should not be a connection between them, sorry
Light flows from LED into phototransitor, making it conduct more through base branch. The increase of current base biases the first Q more making it conduct enough to turn on SCR. SCR shorts out the rest of DC circuit which behaves as a load resistance to AC circuit. Increased curren in AC fires traic which shorts the entire circuit leaving only source, light, triac, and transient suppressor RC. This AC current needs to keep bulb at full brightness when LED is on, and OFF when LED is off. Thing is that i cant get the values to do this. Also, when SCR is off, current flows through both transistor and phototransistor. Can you help me understand how to keep flow from just under firing SCR, and doing so when LED is on. AC resistor values must also play a role. Id appreciate it.
*please note that the negative of bridge rectifier is not supposed to connect to the ground of ac, its supposed to be ground of the dc, there should not be a connection between them, sorry
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