I've been trying to use and SCR to hold a circuit off after the current has reached a set level and cause a comparator to trip and fire the SCR, which should stay tripped, until turned off by another set of conditions. The problem I'm running into is that even when turned on, the SCR still has the customary .7 volt drop, which is enough other components in the circuit to turn on or not turn on as desired. Please look at the simplified circuit, is there another scheme for the use of SCRs? If I add voltage between the SCR and ground in the form of a diode, zener or LED to make the trigger voltage be higher, it also makes it easier for the input to turn it off , my best luck has been to put a LED in the gate lead to force the triggering voltage to above the off plus noise level of the triggering device which also has the .7 volt or more minimum.
It SIMs good, but so far I've had to rebuild the circuit several times and replace the U8 Power PFET a few times, even though the power supply is limited to about 7 amps.
The SCR is supposed to trip when the current from the motor reaches the end of travel and stalls causing the current to rise and stay tripped until the call for the steering motor is removed, causing the and gate to activate.
The above file is 000 Practice 16-12-02.asc, The entire schematic is 000 STEERING-RELAY 16-12-07 CORE + EOT.asc, but you probably won't be able to run the simulation due to components you won't have.
I will appreciate any suggestions or advice you may have, the SCR problem seems to be the last stumbling block, the rest seems to be working great.
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