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Seasonal Circuits

Just a couple of ideas for maybe simple winter circuits.

A battery charger that would charge lead acid batteries automatically maybe once every day or so. Or maybe just charge then float. I thought the charge daily would be almost like a vehicle that is driven daily (battery charge wise). This would be to keep the lawn mower, motorcycle, etc. batteries charged and ready to go.

Another idea would be to take a temperature sensor such as thermistor, rtd, or thermocouple, maybe a comparator and a pot to adjust temperature, attach to solid state relay and use with a room heater. I noticed the thermostats on the oil filled radiators adjust the temperature of the radiator about as much as they control room temperature. Thought maybe with an external sensor maybe it would work better.

RogerN

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RogerN
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Fully charged lead-acid batteries are happy with a 13.8V float charge practically indefinitely. If you're going to put a low battery on it, then you'll need some sort of current limit.

Good Luck! Rich

Reply to
Rich Grise

Do you know how the typically make current limited power supplies? I remember the power supplies we used at school, they had a voltage knob and a current limit knob. Perhaps an adjustable regulator set up for constant current feeding an adjustable voltage regulator? The same circuit to make a float battery charger could make a nice adjustable power supply for hobby.

RogerN

Reply to
RogerN

Generally speaking it's a voltage regulator circuit with a current sensing resistor between the regulator and the load. The greater the current drawn, the greater the voltage drop across the sensing resistor. That voltage drop is compared against a reference voltage. When the current exceeds the limit, the voltage drop exceeds the reference voltags, and the current limiting circuit forces the voltage regulator to lower the voltage.

For example, say the supply is set to deliver 12 volts, with a current limit of 100 mA. If the load is 240 ohms, the supply delivers 12 volts and the load draws 50 ma. If the load is changed to 150 ohms, the supply still delivers 12 volts and the load draws 80 mA. If the load is changed to 120 ohms, the supply still delivers 12 volts, and the load draws 100 mA. But, if the load is reduced to 100 ohms, the load would try to draw more than the 100 mA limit. The current limiting circuit would cause the voltage regulator to reduce the voltage down to

10 volts so that the 100mA limit would not be exceeded. The supply would deliver 10 volts to the load, which would draw 100 mA.

Ed

Reply to
ehsjr

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