electronics question

[m37]

Sorry, I had no idea where to put this question. My observing shed has 2 12v PC case fans to take hot air out during the day so my gear doesn't get too hot. They are powered by a small solar panel and work really well... providing I am there to give them a nudge to get the blades started.

You lot are so clever I thought one of you might know how to regulate the voltage in some way so it won't allow any current through until the voltage gets to, say, 10v. Once they get started they whizz round all day but they don't seem to get started without me there.

I have a huge pile of electronics components (resistors, caps etc) and am reasonably handy with a soldering iron. I was hoping to not spend any money if possible!!!

cheers

[Carl Reade]

You could try connecting a large capacitor or a few across the circuit. + to + and - to - and rated to take the voltage from the panel. It dosnt increase the Voltage rather it acts like a battery and stores charge (current). Motors require more current to start then run. You may have to experiment with different values. Simplest I can think of.

Cheers Carl

[m37]

You could try connecting a large capacitor or a few across the circuit. + to + and - to - and rated to take the voltage from the panel. It dosnt increase the Voltage rather it acts like a battery and stores charge (current). Motors require more current to start then run. You may have to experiment with different values. Simplest I can think of.

Cheers Carl

thanks matey

[m37]

If anyone was remotely interested in this little project or wants a battery-free shed/observatory fan for the summer months I think I got it sussed (finally). 2 x 120mm 12v PC case fans (£6), 12v solar charger from Maplin (£15), 4700uF 35V electrolytic cap (£1.39). Seems to be roasting along nicely and shed is noticably cooler with the sun on it. I'll let you know if the shed burns down. Total cost £22.39.

Christoph.

[Carl Reade]

Is the cap kicking the fans in?

Carl

[m37]

Hi. Without more rigorous observation I won't know for certain but I was here most of the day the other day and I heard none of the high pitched whining they usually omit when struggling. Instead they went straight from off to on.

Looks promising.

[Carbon Brush]

Another option requires a zener diode, a transistor and a couple of resistors. At 10V (ish) the zener conducts, turning on the transistor which in turn powers the fans. Sorry I can't draw it using this keyboard!

[m37]

Thanks Mr Valentine! I read about that but will look into it further.