Increasing Current of 555 timer
Increasing Current of 555 timer
I have a 555 running in the astable mode and would like to have it drive a 5 amp 12 volt lighting load. Being a novice can someone suggest a transistor/mosfet circuit to do this. Thanks in advance.
Re: Increasing Current of 555 timer
Use an IRLIZ14G, available from Digi-Key. Connect the gate to the 555 output, source to GND and lamp load from +12 to drain. Power disapation is about 1 watt so should not need a heat sink.
Re: Increasing Current of 555 timer
Russ if I understand correctly, I would run 12 volts to the lamp and run the ground of the lamp to the drain of the IRLIZ14G? And no other components are needed such as resistors.
Re: Increasing Current of 555 timer
Right. The FET is a voltage operated switch and does not draw any DC current at the gate. If there is much distance between the 555 output and the FET gate, say 1 foot or more, put 10 ohms in series to damp any ringing.
Re: Increasing Current of 555 timer
Watch out for a possible fly in the ointment. If the load is made up of incandescent lamps, the cold resistance is usually much lower than the hot resistance. That lamp load may be much more than 5 amps when the lamp is turned on. This may require a larger FET or a heatsink.<p>That starting surge may afect your power source. I once had a problem where the incandescent indicator lamps were enough load to trigger the foldback current limiting on the power supply, depending on how many were on when the power came up. Sometimes it worked, sometimes it didn't. At least LED's don't have this problem.
Re: Increasing Current of 555 timer
Thanks guys for the help. No problem with distance, all mounted on a small circuit board. This will be used in a automotive application so I will not have the power supply problem and will be used with LED arrays, so should not have the cold filament problem. 5 amps is very worst case and will be more like 3 amps. I assume there is no minimum load for the IRLIZ14G.
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