Derek,
If your fan is rated at .34 amps, and your solar panel is rated at 300 mah (.3 amps),
Well, I thought you were a long ways off, but it sounds like you are quite close, especially since the fan does actually run if started by hand.
I would recommend testing everything rather than taking the manufacturer's word.
Put the fan on a 12V battery (either car battery or 2 x lantern batteries). Check the power consumption (amps) with your digital ammeter/multimeter.
Also, test your solar panel when connected to a not quite fully charged battery, or when connected to your motor.
What you will probably notice when testing the fan is that it's power consumption will spike early, then level off as it comes up to speed.
There may be a way to design a circuit that would use a capacitor to create an initial boost... then turn it off. Unfortunately, I can only visualize half the circuit.
You might consider:
Battery Backup (which should provide the starting power needed).
Turn on and off the fan with either a separate photo sensor/detector, or a mercury thermostat.
I'd have to review thermostat design, but a mercury thermostat is dependable, and uses ZERO POWER, but only works at a static temperature setting.
I wonder if there is a way to set 2 thermostats, one in the house, and one in the solar panel to only activate your fan when it is warmer inside the panel than inside the house, hopefully not tripping the fan on and off all the time, and actually being able to shut the fan off at night rather than continuing to blow warm air through, heating your thermostat.
Maybe an answer would be the battery and solar cell, a mercury thermostat set at 65 or 70 degrees, and a photo detector.
Ummm... it is sounding too complicated....
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What about a circuit like this:
Solar Array (no battery)
- - ------------------------------------------------> - Motor
- + ----------------------------------------------> |- + Motor
- + --> Capacitor --> Mercury Thermostat --> |
+ Motor
There might be advantages of using a two pole mercury switch so that power isn't sent to the motor until the temp rises and throws the capacitor circuit. But, the problem might be an instability with starting and stopping such a circuit too frequently (although, the mercury thermostat would naturally have a few degree range on/off cycle and you certainly don't want to cool your house on a cloudy day).
In your case, you could test the circuit with:
- - ---------------------------------------> - Motor
- + ------------------Two Pole Switch --> |- + Motor
- + --> Capacitor --> Two Pole Switch --> |_ + Motor
I don't know the rating of the capacitor, but I am sure there is someone here with better electronics skills that would have a suggestion.
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When I looked up capacitor start AC motors, they discussed having a starter winding (often with a centrifugal shut-off switch).
You might be able to do something similar with a super small motor attached to the larger motor.
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As far as diodes, all of my solar panels (Siemens) have low loss diodes built in. Presumably they are symmetrical in their power generation and could send the power either direction if the diodes were removed. In fact, they seemed to have a slight tendency to send power backwards when I bypassed the diodes. I am not sure why they had two diodes (+ and - poles) rather than a single one. Maybe I should go around and scavenge the redundant diodes.
---- Clifford -----
