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555 intermittent motor control

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quacker

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Novice in need of help. I want to control a 3 V (2AA) electric motor with 2 +/- sec on and 50-60+/- seconds off. Know that I should use a 555 for control. Found a project at **broken link removed** that is a 555 controller. Was thinking about switching the capacitors and resistors to C=200uFd, R1 to 15,000 ohms, and R2 to 400,000 ohms, and hooking the motor up to where the lights would connect. I was also told I will need a power MOSFET.
Will this work? Are these reasonable Capacitor and resistor values (just plugged values into calculator until I had the right timing)? If I need a Mosfet, how do I size?
Thanks in advance.
 
What supply voltage do you want to run this on? If 3V, that poses some problems. Only CMOS versions of the 555 will operate properly on 3V. Most Power FETs will not turn on with only 3V on their gate, so you would have to use an NPN switching transistor. How much current does the motor draw when powered from 3V? Be sure to measure the starting current as well as the running current.
 
The voltage to the 3 V motor is 12 amp when running.
I also have a 6V motor that runs at 46 amps.

Another question. Will a 555 timer drain down a battery the same amount as leaving the motor runing continuously since it is charging the capacitor?
 
Are you sure about those motor currents, as they seem way too high for those voltages? The quiescent current for a 555 is totally insignificant compared to the 12A or 46A motor draw. What are you trying to do...the whole project?

ken
 
Seriously high currents, at that sort of rating, you will generate tons of heat at the switch.

Recheck the values.

If they are the values, then as Kmoffett says, 555 timer wont cut it. You'll have to look for a better IC which can deliver more current and a Power MOSFET.
 
Sorry, those are mamp values.
What type of 555 will I need?
Should I go with the 6V motor instead of the 3V?

Thanks
 
Hi quacker,

if you use the 6V motor you can use an NE555 timer circuit.

The attached circuit should work for your application.

Not contained in the schematic: decoupling capacitor for the NE555! Use a 47 - 100µF electrolytic cap for the power supply and 100nF connected to the supply pins of the timer IC.

Boncuk
 

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