Solar Powering a quartz clock motor

[nic_marsa11]

Hello everyone,

I'm starting a personally exciting venture into solar panels. However my knowledge is limited so be kind, but I've no idea where to get some. So i turn to you.

My project is to rotate an object outside once every 24 hours indefinitely. I thought I'd power a sealed quartz clock motor with solar energy. However aside from a 150µA @ 1.5V quartz clock motor from maplins and a mini 1.5V solar panel (0.5A though, too much?) I've stuck on what other items i need.

Is it as simple as buying a rechargable AA battery and connecting it to the solar panel and motor? At night, will the solar panel have charged the battery for it? Or do i need something for the panel to charge the battery first before powering the motor?

Thanks very much

Nic

 

[Hero999]

0.5A is way overkill but it shouldn't damage the clock motor because it will just dray as much power as it needs.

With a current draw of just 150µA you should consider using a 22F supercapacitor rather than a battery.

Increase the solar panel voltage to 1.8V (to make up the diode loss), connect a low leakage Schottky diode in series with the solar panel, the the capacitor between the diode and 0V and the clock across the capacitor.

With a 0.5A solar cell the capacitor will charge to 1.5V in just over a minute.

I'd recommend using a smaller solar cell, simply because it's cheaper and lower current diodes will have a lower leakage current. A 25mA panel will charge a 22F capacitor to 1.5V in a under a quater of an hour and will enable you to use a very low leakage diode such as the BAT45.

A 22F capacitor should power the clock for 20 hours on one charge assuming the capacitor doesn't leak but in reality it'll be less.

Unfortunately I couldn't find the leakage current of the capacitors sold by Farnel.
https://www.electro-tech-online.com/custompdfs/2010/04/18815.pdf

Supercapacitors are much more expensive than batteries but they charge much more quickly and they simplify the design.

 

[crutschow]

Supercapacitors are much more expensive than batteries but they charge much more quickly and they simplify the design.

How is a supercapacitor simpler to use than a rechargeable battery?

 

[Grossel]

How is a supercapacitor simpler to use than a rechargeable battery?

Caps doesn't require constant current to charge.

 

[Hero999]

How is a supercapacitor simpler to use than a rechargeable battery?

It can be permanently connected to the solar cells.

Modern NiMH batteries tend to be very sensitive to overcharge.

 

[crutschow]

Modern NiMH batteries tend to be very sensitive to overcharge.

True. But if you limit the maximum charge rate to below C/20 that should prevent any long-term damage to the battery, and still give more than enough energy to run the clock when the sun isn't shining.