I have been working on Arduino and stepper motor from Opel IAC valve - standard one which is used on many vehicles around the world including some Volvo and a lot of GM cars. Part number for this IAC valve is A95214. It has four contacts which are connected to two coils. Coil impedance is about 50 Ohms. But I cannot seem to find a reliable source for other technical information about this stepper motor. The only thing I could get is that it is driven by 12 Volts (at least in Megasquirt project). The questions that I have are:
How many degrees will it travel per one step or how many steps there are per 360 degrees? Is there any general rule for this?
Do I need to limit current somehow? The stepper gets very hot even when not moving at all. Do I put some kind of resistor between SN754410NE and stepper motor?
Is there a way to "tell" SN754410NE to stop outputting current when there is no movement?
Does it make any difference if I swap 3 and 6 and/or 11 and 14 output ports of SN754410NE?
Is there a way to connect Arduino via some kind of buffer/optocoupler interface to car and read original signals (polarity, amps, duration)?
A stepper motor needs to have power all the time, or it will go "limp" and let the load move the shaft every which way.
If 12V makes it run too hot, try powering it with less voltage, or try using a PWM control signal to reduce the torque (and thus the power, and thus the heat.)
Can you read external signals with an Arduino? Yes, you can! Make sure to get the proper grounding and reference (if it's a known signal) or isolation (if it's an unknown signal.)
If the signal is very fast (say, a fast pulse or PWM signal) then the Arduino may have trouble keeping up.
Thanks.
For purpose of just-for-fun I do not really care if it goes "limp" - I rather do care about temperature so that it does not burn. What do you mean by PWM signal? Isn't using SN754410NE or L293D the same as using PWM signal? I mean shouldn't the stepper coils take the needed amount of power themselves?
About signal reading - is optocoupler used for this? Something like 4N25? Will it work with changing polarity?
The stepper coils will take "full power" while they're on. It may be that the device is immersed or otherwise cooled while it's operated in a vehicle, and thus is designed to dissipate a lot of heat.
I don't know that the controllers you list do PWM as such -- they may micro-step, but still at full possible power, rather than making a duty cycle that delivers less torque. The easiest fix is to reduce power from 12V to 10V and see how it goes.
Finally, you can use an opto coupler for some kinds of sensing. Or an opamp. Or a resistor ladder. Or one of a zillion other mechanisms. It all depends on what you know about the signal you're sensing.
Thanks.
Ok. But total newbie question - if I put 50 Ohm resistors on each output wouldn't that limit current to 0.12 A? So total power would be around 1.44 W. The controller I took was from Arduino's own Tutorial right here. I found some AC-in optocouplers - I hope I can use them.
i try to control my IAC and i don't know what is the suitable driver to connect with it and depending on what to choose the driver?