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Temperature Sensitive Switch For Solar Collector

This circuit can be used to turn the pump on and off when a solar collector is used to heat a swimming pool, for example. This way the water in the collector has a chance to warm up significantly before it is pumped to the swimming pool. A bonus is that the pump doesn’t need to be on continuously. The basis of operation is as follows. When the temperature of the water in the solar collector is at least 10 °C higher than that of the swimming pool, the pump starts up.

The warm water will then be pumped to the swimming pool and the temperature difference will drop rapidly. This is because fresh, cool water from the swimming pool enters the collector. Once the difference is less than 3 °C the pump is turned off again. R10/R1 and R9/R2 each make up a potential divider. The output voltage will be about half the supply voltage at a temperature around 25 °C. C7 and C8 suppress any possible interference.

The NTCs (R9 and R10) are usually connected via several meters of cable, which can easily pick up interference. Both potential dividers are followed by a buffer stage (IC1a/IC1b). IC1c and R3, R4, R5 and R6 make up a differential amplifier (with unit gain), which measures the temperature difference (i.e. voltage difference). When both temperatures are equal the output is 0 V. When the temperature of the solar collector rises, the differential amplifier outputs a positive voltage.
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Read more: http://www.extremecircuits.net/2010/06/temperature-sensitive-switch-for-solar_03.html

Be the first to comment - What do you think? Posted by admin - February 19, 2011 at 12:10 am

Categories: Detector, Electronic Control Tags: solar controller schematic, Solar power systems, temperature sensitive switch

DC motor runs off of calculator solar cell in dim light

How do we achive 10nA operation? By using diodes in place of pull up resistors, and by isolating the DC load from the trigger circuit via junction drops and the 10nF capacitor. If there is too much power comming from the solar cell then the motor might run too often or even continuously. You can avoid this by putting a 100K ohm resistor in series with the solar cell.

Be the first to comment - What do you think? Posted by admin - July 2, 2008 at 1:38 pm

Categories: Electronic Control, Lighting Tags: Light relay switch, motor control, Solar power systems

PowerSmart Solar Speeder Motor by 2N3904

This must be the most efficient bipolar transistor motor driver design for this application and I recommend it for the solar roller competitions. A 1381E is used to trigger at 2.4V. While it takes a total of 10 components plus motor compared to the stock circuit’s 6 components, you will clearly get better performance compared to a stock Solar Roller/Speeder circuit.