in my attachement, you can find the circuit. It is very simple. All I want to do is to control my motor. Here comes the problem and I really have no clue why this happens.
When I measure the voltage between 1 and 2 and the motor is not in the circuit, i get 6 Volt. Now I put the motor in. Normally it should start to spin. But it doesn't. I measure again between 1 and 2 and I get 0 Volt.
Why? When I put the motor directly on the 6V batterie pack he spins. But when I want to use the motor in the circuit to control it, it doesn't spin, although the circuit works perfect.
The BC547 will only handle low currents up to 100mA. That is nowhere near enough to run any practical motor I've ever seen. Even tiny pager motors need more than that on startup.
einspluseins:
So I need a different transistor? Can you tell me which one i need? (I just measured the motor current, it is 2.4 A.)
Probably a good option is to use a n-channel mosfet transistor.
The other thing is..... when designing circuits, know as much as you can in advance about what sort of components you need. From what you had been doing, it just appears that you didn't understand what that particular transistor (your bc547 NPN bipolar junction transistor) was capable of..... or not capable of.
einspluseins:
So I need a different transistor? Can you tell me which one i need? (I just measured the motor current, it is 2.4 A.)
2.4A? No chance whatsoever of driving that from an Arduino with just a BJT, since the Arduino
pins can't output the 0.2A needed for a suitable power device. BJT's as switches need about 5 to 10%
of the load current into the base. The DC current gain isn't relevant for saturated switches.
Your options are darlington (which will definitely need a heatsink at 2.4A), or logic-level MOSFET,
which is much better (can run very cool with the right device - low on resistance).
einspluseins:
(I just measured the motor current, it is 2.4 A.)
Was that reading taken with the motor spinning free in the air? It will draw more with any significant load. And a LOT more when stalled (prevented from turning while being fed power).
Here's a pic of my cheapo door lock motor stalled.
dougp:
Was that reading taken with the motor spinning free in the air? It will draw more with any significant load. And a LOT more when stalled (prevented from turning while being fed power).
Ty for checking this out. The reading was taken with the motor not spinning free in the air.
I tried IRL540 and FQP30N06, as well as BUK9535-55. All with a 220R and 470R base resistor and with no resistor. With all comes the same problem:
When i put the pwm level to 100%, then i measure a voltage of 6V at the motor terminal. When i put the pwm level to 1%, i measure 6V, too.
einspluseins:
I tried IRL540 and FQP30N06, as well as BUK9535-55. All with a 220R and 470R base resistor and with no resistor. With all comes the same problem:
When i put the pwm level to 100%, then i measure a voltage of 6V at the motor terminal. When i put the pwm level to 1%, i measure 6V, too.
Then something is wrong with the wiring of your circuit. Are the grounds common? Is every connection
sound (ie did you check continuity with a multimeter?). Is the device connected correctly according to
the pin-out? Did you measure the gate voltage with a multimeter to ensure the 5V was getting to the gate?
Hi,
Have you looked at the data sheet for your IRL540, FQP30N06 and BUK9535-55 and checked the pin allocations.
Can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png for the MOSFET?
So, I just figured out what the problem was. I measured the no-load voltage. Say without the motor in the circuit. But when I put the motor in, it works. I can control it.
But I don't know why the no-load voltage is always 6V. When I measured the no-load voltage when there were a transistor and not a mosfet in the circuit I got measured data from 0 to 6V.
