I found a circuit on the web that I wanted to build using the parts I had on hand. The changes I made were (1) used 1N4148 diodes instead of 1N5818, (2) used a 10k pot for VR1 instead of a 100k and a 1uF cap for C1 instead of a .1uF, and (3) am driving a red LED instead of the gate of a IRFZ46N Mosfet.
I I breadboarded the circuit and it works; I can adjust the brightness of the LED using VR1. My questions are as follows.
1. The LED goes very dim, but not completely off. Is that normal? (ETA: When I inserted the 510 Ω current limiting resistor, the LED then would go almost completely dark, so I guess my question is answered.)
2. I think perhaps the 10k resistor was only a pull-up for the gate of the MOSFET. Does it serve any purpose with the LED or should I delete it? (The circuit seems to work without it.)
3. I added a 510 Ω current limiting resistor in series with the LED and that seems to limit the current to 20 mA. However, does my DMM measure the current correctly when it is PWM'ed? (I don't seem to be able to measure the voltage drop across the LED.)
Thanks.
I I breadboarded the circuit and it works; I can adjust the brightness of the LED using VR1. My questions are as follows.
1. The LED goes very dim, but not completely off. Is that normal? (ETA: When I inserted the 510 Ω current limiting resistor, the LED then would go almost completely dark, so I guess my question is answered.)
2. I think perhaps the 10k resistor was only a pull-up for the gate of the MOSFET. Does it serve any purpose with the LED or should I delete it? (The circuit seems to work without it.)
3. I added a 510 Ω current limiting resistor in series with the LED and that seems to limit the current to 20 mA. However, does my DMM measure the current correctly when it is PWM'ed? (I don't seem to be able to measure the voltage drop across the LED.)
Thanks.
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