Thanks, so yeah, I meant that I used the pin with the ~ line (6) and also, I connected it the way you told me, (collector to one side of the motor, emitter to ground, and other side of motor to positive on the battery).It still doesn't do anything. I'm not sure then if it might be the transistor that is malfunctioning. For the schematics, I don't know how to draw schematics on here. Btw, I've copied exact circuits from others explaining it, but it still doesn't work.
What is the type and part number of your transistor?Can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png?I think this is how you should connect your motor.Tom..
150 or 220 ohm base resistor, don't bother with 1k. You want as much base current as the Arduino pin can safely produce - transistors as switches need a base current that's 5 to 10% of the load current.
A 220 Ohm resistor is needed when lower HFE transistors are used. Don't get me wrong, it will work but why push the Arduino output to the limit ?
On the other hand most diagrams recommend a 1K base resistor. 1k base resistor will work just fine on high HFE transistors such as the BC337 or the 2N2222. Darlington transistors are also good choice.
You can always measure the Base-Emitter, Base-Collector and Collector-emitter voltages to verify that the transistor is fully on and fully off. You want to use the transistor in saturation mode and in cutoff mode, not in the active region in between.
...So your 1k resistor feeding 4.35 mA to the transistor base can hold it in saturation for no more than 87 mA.
if for example we wanted to 'limit' the ICE, might using a "high(ish)" resistor be the way to go ?
if for example we wanted to 'limit' the ICE, might using a "high(ish)" resistor be the way to go ?let's say we wanted to "hold back" the motor from going full blast - or would that be better acheived by using a lower PWM duty cycle and not use the transistor in the 'active region' unnecessarily.
A 220 Ohm resistor is needed when lower HFE transistors are used. Dont get me wrong, it will work but why push the arduino output to the limit ?
What limit? 4.35 V over 220 Ohm is 20 mA, a common current used to illuminate LEDs brightly. Nowhere near the absolute maximum rating which I do not even mean to cite - since doing so tends to lead foolish people to fantasise that is an acceptable target to use. So you didn't read MarkT's explanation?(I have to chuckle here. "most diagrams" - on "Instructables" perchance? )Oh, so you do have some knowledge about "saturation mode" in which Hfe is irrelevant, so why do you talk about "high HFE transistors"? Mark has explained that you need at least 5% of the collector current, that is, a gain of 20 at best for saturation.So your 1k resistor feeding 4.35 mA to the transistor base can hold it in saturation for no more than 87 mA.
No, sorry, that's a myth. Hfe is irrelevant to saturation. In saturation the base-collector junction is forward biased and there is _no_ conventional transistor action, just carrier diffusion from emitter to collector due to the carrier concentration gradient. Emitters are doped about 100 times more strongly than bases and bases about 100 times more than collectors, leading to a large concentration gradient which drives the action, not an electric field.I suggest you go read a few datasheets on switching transistors which quote all the Vsat and relatedvalues and graphs with "Ib = 0.1 Ic" or "Ib = 0.05 Ic"
20mA may be perfectly safe for a single pin but it is not the only limit. The whole ATMega has absolute maximum rating 200mA and there are the strange limits of total current for groups of pins.