Thanks, I guess what I need is a circuit that could automatically activate the motor when the sun is out. It is set up on a solar heater I made and I won't be around to connect it to the motor when it's needed. Do you or anyone know what type of circuit that would be called so maybe I can find a schematic to follow? I've got the most basic of knowledge in electronics, but I have a bunch of components. Perhaps I can build a circuit for this task.Yes, if you charge the capacitor from the solar panel without the motor connected then connect the motor to the charged capacitor and the solar panel in parallel. The capacitor will probably need a high value.
I don't suppose I could use this mosfet in a different circuit could I? https://www.infineon.com/dgdl/irfz44npbf.pdf?fileId=5546d462533600a40153563b3a9f220d I have 10 of them! But I think it's a different style...I don't know what a QFET is.What is the open circuit output voltage of your PV? Can it actually supply enough current to run the motor, just having issues with starting? Perhaps something as simple as this:
No, there is nothing to sense the voltage on the capacitor then turn on the Mosfet so the Mosfet slowly turns on too soon, before there is enough charge in the capacitor. You need the Mosfet to turn on suddenly at the correct voltage, not slowly at a voltage that is too low.The mosfet is off until the voltage across the capacitor is >10 volts, at which point it turns on and allows the capacitor to assist with the current surge require for the fan to start. Once it is started, as long as the PV is generating enough to run the fan, it will keep running. If the PV is not generating enough, it might end up going on and off and on and off.....
The MOSFETs Vgs(th) and the resistive divider determine at what point the power starts to come on. Probably want to set that so that the MOSFET starts to come on at about 75% of the maximum available voltage. You are absolutely correct that it will start to come on slowly, and waste some power, but I think at start there may be enough energy stored in the capacitor to get the motor going. Then as long as the PV outputs more than the motor uses, the voltage on the cap will continue to increase and MOSFET will end up fully on.No, there is nothing to sense the voltage on the capacitor then turn on the Mosfet so the Mosfet slowly turns on too soon, before there is enough charge in the capacitor. You need the Mosfet to turn on suddenly at the correct voltage, not slowly at a voltage that is too low.
I have wired up a 12V computer fan that can only run through my small solar panel if I start it with my fingers
Burt may be correct.Think the op needs to find a better fan first.
It is as you say, solar cell too small, fan too big. I would guess most poeple here already know that. The trick is, how to overcome this problem with what I have available. A possible solution has been given and I am currently working on locating the parts needed to try it out. I will let everyone know my results, or troubles in making this circuit.Burt may be correct.
What is this recent fascination with trying to power fans from a solar cell?
I got a 2.5W 5V/500mAh solar panel, which reads 5.7V under a full sunlight, and a 3V-12V DC motor, which someone said in a comment that at 3V no-load takes 35-40mA. If I wire the motor directly to AA battery reading 1.23V, it spins fast. But when wired directly to the panel, it won't spin at...www.electro-tech-online.com
Solar cell too small, fan too big.