maybe it's something you would need to tweak on pin 6
Your meter cannot properly measure the voltage pulses.
How do you guys know he is using a Volt meter at the gate of MOSFET ? He does not actually mention anything on how he is measuring it. What if he is using a scope ?2.5V measured in DC range means that the gate pulse duty cycle won't go below 20 %, presuming the circuit is operating correctly.
Hi guaravkothari23,
Could you check you've put this circuit together correctly (no "Oh my God, look where I put that wire/component, I hadn't noticed before." kind of stuff)?
I made it on a breadboard, admittedly using an LED instead of a motor, and a logic level MOSFET - I have some IRF520s but don't see much difference as the circuit should work with most things. It's on a "12V" supply, that gets to about 11.76V. I changed 1k for a 10k, used 1N4148s for the diodes, and I think that schematic may have an error: pin 5 is usually a 0.1uF, not 0.1nF capacitor to ground.
I get with the DMM on DC voltage setting:
LED on: pin 3 and pin 7 = 11.4V, MOSFET drain = 0V
LED off: pin 3 = 5mV, pin 7 = 14mV, MOSFET drain = 10V
Cheap oscilloscope on DC and VMAX settings shows pin 3/7 go from solid line at 10V through squarewave duty cycle that is wide on time then narrower and well-spaced apart on time pulses until it becomes 0V flatline.
That circuit should work AFAIK. It can certainly power an LEDIf you have everything right and it's not going below 2.5V, how about shoving a BJT or another MOSFET between pin 7 and the MOSFET controlling the motor path to ground? Obviously needing to make one P and the other N. It might not work but it might make some difference.
without load i cant drop the voltage below 2.5V
Hi. That looks like TINA. Did you have to modify three analysis parameters (TR max iteration number, TR truncation error factor and TR maximum time step) to get the 555 to simulate? Thanks.
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