Hi guys, could someone draw me a simple circuit please?
I want it to light a bulb for approx 2-3 seconds when powered, and then the bulb to go off while the circuit remains powered (12volts)
I havn't a clue regarding electronic theory, but can follow instructions well.
Thanks
Dave
Here is a circuit I just thought of. It uses a P channel mosfet as a high side driver. Initially the capacitor is discharged and the mosfet is fully on, as the capacitor charges the mosfet will turn off.
Try this one. Uses my favorite part, the LM431. It does the delay each time power is applied, and resets when power is removed, even for a short time. It is the input bias current of the LM431's opamp that charges the timing capacitor. The capacitor discharges through the diode, the lamp, and the 10K resistor.
Here is a circuit I just thought of. It uses a P channel mosfet as a high side driver. Initially the capacitor is discharged and the mosfet is fully on, as the capacitor charges the mosfet will turn off.
It works once when the capacitor is discharged. However, when the 12V is disconnected, there is nothing to discharge the capacitor. I had to add the diode and resistor to discharge the timing capacitor for each subsequent cycle.
Mike,
Your first circuit might overheat the TL431 because the current exceeds its absolute maximum rating of 100mA, the lamp's current should be lower, use an LED and a suitable current limiting resistor.
Here is a circuit I just thought of. It uses a P channel mosfet as a high side driver. Initially the capacitor is discharged and the mosfet is fully on, as the capacitor charges the mosfet will turn off.
Mike,
Your first circuit might overheat the TL431 because the current exceeds its absolute maximum rating of 100mA, the lamp's current should be lower, use an LED and a suitable current limiting resistor.
hi there i'm new here...i've got sort of similar problem like op but really dont want to hijack the thread but how do i create a new post pls? or should i just forward my circuit diagram here? pls help TIA
hi there i'm new here...i've got sort of similar problem like op but really dont want to hijack the thread but how do i create a new post pls? or should i just forward my circuit diagram here? pls help TIA