Hi,
I'm using a simple 555 monostable circuit to control automatic shutoff of another circuit. The problem I'm running into is the R/C calculations given result in vastly different duration then what its supposed to be. Anyone have an idea of what could be the problem? I'm currently using the attached circuit with one modification I'm using a 0.01uf cap on pin-5 to gnd. My output pin 3 is connected to a N-channel mosfet. I have used other similar circuits to this one and I'm getting the same results. Currently my R1 is 4.7Meg and C is 220uf. I believe this should result in a 1137.4 second (18 minutes) on cycle. But its currently giving me about 2100 second (35 minutes) on cycle.
I have used a few different 555 chips so I dont think its a problem with the chip. Also Im using a 12v source from an old UPS battery as my power source.
any ideas?
Thanks!
I'm using a simple 555 monostable circuit to control automatic shutoff of another circuit. The problem I'm running into is the R/C calculations given result in vastly different duration then what its supposed to be. Anyone have an idea of what could be the problem? I'm currently using the attached circuit with one modification I'm using a 0.01uf cap on pin-5 to gnd. My output pin 3 is connected to a N-channel mosfet. I have used other similar circuits to this one and I'm getting the same results. Currently my R1 is 4.7Meg and C is 220uf. I believe this should result in a 1137.4 second (18 minutes) on cycle. But its currently giving me about 2100 second (35 minutes) on cycle.
I have used a few different 555 chips so I dont think its a problem with the chip. Also Im using a 12v source from an old UPS battery as my power source.
any ideas?
Thanks!
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