This is driving me insane. - I've tried a TIP31 (lights dimly) and an IRF730 Basically, I have a 12v rail, which goes to the collector (12+) 0 to ground, the circuit is fine, if i feed 12v directly from the rail, both transistors light up the 12v bulb... but, connect the 5v to the transistor, the t…

5V is a marginal Vgs for the IRF730. It needs more. See circuit / attachment. [NPN&mosfet.JPG]

ahhhhh, thank you, i'm so glad it can't be done I honestly thought i was going mad lol Thanks for the circuit :slight_smile: - muchos gracias senor.

For this reason I almost exclusively use logic level MOSFETs, that is, MOSFETs designed to be driven by the relatively low voltage of 5V. I like the 12N10L from Jameco, part # 1071214 $0.65. Costs a little more but saves time and extra parts.

Is this how you had it hooked up? +12 -> bulb -> TIP31 Collector Arduino digital OUTPUT pin -> 80 (or more) Ohm resistor -> TIP31 Base TIP31 Emitter -> +12 Ground -> Arduino Ground Did you remember to set the pin as an OUTPUT? Did you remember to set the OUTPUT pin to HIGH? The TIP31 DC Curren…

cjdelphi: This is driving me insane. - I've tried a TIP31 (lights dimly) and an IRF730 Basically, I have a 12v rail, which goes to the collector (12+) 0 to ground, the circuit is fine, if i feed 12v directly from the rail, both transistors light up the 12v bulb... but, connect the 5v to the trans…

Your description is unclear. Do you have the load connected: (a) between the drain of the mosfet/collector of the TIP31 and +12v; or (b) between the source of the mosfet/emitter of the TIP31 and 0v? Method (b) will not work because only 4V or less will get passed to the load using the TIP31, and …

What is the bulb? Bulb filaments take significantly higher currents at start up than when hot (up to 10 times as much) so you have to rate the transistor or MOSFET accordingly. The IRF730 is an odd choice of MOSFET - 400V rating and far too high an on resistance (1 ohm) for a low voltage circuit. Y…

dc42: Your description is unclear. Do you have the load connected: (a) between the drain of the mosfet/collector of the TIP31 and +12v; or (b) between the source of the mosfet/emitter of the TIP31 and 0v? Method (b) will not work because only 4V or less will get passed to the load using the TIP…

[arduino blinker] 500ms delay [pretty] 100ms delay.

Nice. I'd say you figured that one out.

Control a 12v from 5v.

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Control a 12v from 5v.

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