Start and stop a 3 volt dc motor every 5 seconds

P

peter p

New Member

• Mar 16, 2013

• #1

Hello,
is there a switch I can get that when I switch it on will start a 3 volt motor and run for 3 seconds then shut off for 3 seconds, start for 3 seconds etc, etc,.
It needs to run like this until I switch it off.

If there is no switch that automatically does this then is there something I can make to do this?

Thanks.
Peter

 

ronv

Well-Known Member

Most Helpful Member

• Mar 16, 2013

• #2

It will be pretty easy to build something, but we will need to know the current of your motor as well as the voltage. Is the power batteries?

If you don't know the current a size might help.

 

P

peter p

New Member

• Mar 16, 2013

• #3

The motor runs on 2 AA batteries.
Its a small motor from a hand held fan.
I'm making something with it and need some sort of delay on it.

The current is DC.

Peter

 

Last edited: Mar 17, 2013

MikeMl

Well-Known Member

Most Helpful Member

• Mar 17, 2013

• #4

Since you have only 3V to work with, this makes it complicated.
First, the switching device must have a very low ON resistance, so that the voltage drop across it doesn't subtract from the battery voltage. A FET comes to mind.
Second, you will have to use the special CMOS version of the 555 timer chip to implement the 3s on/3s off mulivibrator becasue the standard one will not operate below 4.5V

 

alec_t

Well-Known Member

Most Helpful Member

• Mar 17, 2013

• #5

Assuming you want 3s on/ 3s off (contrary to the title of your post) and can't get hold of that particular 555 you could use a CD40106 (or CD4093) instead, like this :-

 

MikeMl

Well-Known Member

Most Helpful Member

• Mar 17, 2013

• #6

Alec, according to the datasheet, the 2N2222 has a max Vce(sat) of 1V, which is too high. An NFET would (it would have to be one with a low Vth) would likely have less than a few mV drop when turned on....

 

alec_t

Well-Known Member

Most Helpful Member

• Mar 17, 2013

• #7

@MikeMl
You're quite right. My bad. Vce(sat) was much lower in the sim and I didn't check the datasheet