Replace the motor with an LED (and appropriate resistor) to see if the timer still works. Don't get your hopes up!

You'll need a transistor - I'd use a MOSFET, I have IRF540N on hand and it would be fine - to take the control signal from the timer and control the current through the motor.

Your diode should be rated to 6A, if the 2X guideline is followed. 6A04 is an option, or this.

 

Doublecheck: Yes, IRF540N will work.
It isn't a logic level mosfet, but it is well within range to carry 3 amps at 5Vgs.

 

Does it make sense that a tape measure uses a 3A motor? I guess that's the stall current, but it still seems like a lot.

Oh, and I'm not really recommending the IRF540N, just pointing the OP towards a MOSFET datasheet. I think with the voltage at the timer output, he should probably look for a logic-level MOSFET. The Shack has the IRF510 in store usually, which is not logic level either but might work just as well (or poorly?) as the IRF540N.

 

From the picture you show with your meter connected, you have it connected to the two motor leads. If so, that is NOT correct. You are measuring how much current the batteries can put out! The meter needs to be placed in series with the motor. The easiest way to do that is to put your leads across the wires going to the switch. (the meter will complete the circuit instead of the switch)

 

That's just what I was thinking, "Does it make sense that 4 AAA batteries would be harnessed to a 3 amp motor?"

 

Okay so i took all your advice and hooked up my amp-meter to the switch and let it complete the circuit.

so the amps seem to increase as t increases (due to the force of pushing out the tape i'm guessing)

Starts at 1.297 A
and finishes after 5 seconds at 1.722


*Am i still running with a IRF510 or IRF540N?

besides from this diode, am i missing anything else in the circuit. Im going to buy a new NE 555 just in case.

 

Get some new batteries too. Yours are showing signs of being tired.

 

so do ill need a transistor or a diode?


running at 6V and 1.297-1.722A

 

so do ill need a transistor or a diode?


running at 6V and 1.297-1.722A

So, I guess the big question is, what happened to the Transformer, why are you still using batteries?

Power wouldn't be a problem?

I like the Thread but, I'm confused.

 

The tape measure originally came with (4) AAA batteries.

And yes, you need a mosfet and a diode.

 

So i canned the battery conversion, just want to get this trigger up and running than will worry about the power supply later !

@Killivolt i am probably just as confused as you even more and im building the thing!.

So @#12, i'm so sorry to keep bugging you guys and i really do appreciate all the help, so i know where i need to put the diode, where do i put the mosfet?

 

IRL530 is logic level, Any motor circuit without speed control or current limiting, current will be proportional to RPM (load).
The stall current will be limited to whatever the resistance of the armature and brushes is.
Max.

 

There is more than one way to skin this cat.

 

Alright so round 2 of building this circuit. I restarted tonight to make sure everything was in check.

Went to the shop and purchased

Another Timer (NE555)
ZR1029-Diode MBR735 SCHOTTKY 35V 7A
ZT2466-MOSFET IRF540N 100V 33A TO220AB

the IRF540N was all they had.

View attachment 59283















This time things are allot better, no heating or anything its just that as soon as i connect the source the motor runs (without switch pressed or even integrated in the circuit) i replaced the 555 with the new one and all. i RAN the motor for 20 seconds on both ends of the variable resistor to see if it would cut out,

I just dont understand why the motor turns on straight away once i connect the source and doesn't even wait for the trigger or button to be pressed.

Thanks Guys. good luck

 

I can not see any inverter transistor in there. You bought N-MOS drivers and did not invert the output of the 555 so it would wait for you to push the start button.

As you can see from the drawings I made, 2 ways to skin the cat, you can either use a P-MOS driver or add an inverting transistor and use an N-MOS driver.

The inverting transistor can be any old, ten for a dollar, PNP transistor of the smallest size. I don't think you can buy one that isn't good enough for this job.

 

You'll find them in just about everything.

PN2907A.

 

Okay so i went out and bought a P channel MOSFET (http://www.irf.com/product-info/datasheets/data/irf9540n.pdf)
and plugged it into where my N-channel one was. AND now nothing happens except for the P channel MOSFET getting hot. I press the button but it doens't engage the motor, i fiddled with the POT but it didn't change anything.

If i put the N channel back in its business as usual and the motor just keeps running.

View attachment 59305

 

Okay im stumped. Does anyone have a clue what is going on with my circuit. I have re wried it 3 times and still the same result.

 

Probably a weak choice of P-fet. Good ones can be expensive. Better try an inverting transistor with the old N-type mosfet. (The second drawing.)

 

is it okay to use a Schottky diodes instead of a snubber