I am totally new at this. I just learned AI is no help. It had me trouble shooting a circuit it gave me for three days now before finally admitting the circuit was no good.
I've learned a little bit. I am wanting to regulate the volts from a solar panel down to 12v so's it can feed directly into a tiny 12v pump. I'm happy to waste the excess and happy to avoid batteries and regulators.
The circuit i have is just a TIP122 is all. A cap across the input. And here's the thing: AI stipulated a 15v zener and a 1k R in series between collector and base. That's what we never could get working.
Seems from what I think I've learned that the R should be between collector and base and the zener between base and the neg rail which runs straight from source to load, the pump.
Is that right? And if so is 1k ohm for the resister about right and a 15V 1W zener?
It is a tiny 12v pump and the panel is supposedly a 12v panel but puts out up to 20v when its raging.
If there's a place to look up circuits like this I' like to know about it. I'd look them up.

 

hi abro,
Welcome to AAC.
Do you have a circuit diagram you could post?
E

 

"Need a simple circuit for dc low voltage regulator"

I'm happy to waste the excess and happy to avoid batteries and regulators.

You want a regulator to avoid regulators? This seems unlikely, what did you mean here?

What is the current requirement (stalled)?

 

If I understand your requirement correctly you are about right with your suggestion. A resistor from the panel to the base of the darlington pair and 15V zener from the base to ground should give you around 12V at the emitter. Connect the pump between the emitter and ground. Connect the collector to the panel. You don’t really need a darlington pair, just an NPN transistor will do and you will only lose 0.6V across the base to emitter instead of about 3V which means the pump will probably keep running when the panel output is lower. And use a 12.5V zener

 

I am totally new at this. I just learned AI is no help. It had me trouble shooting a circuit it gave me for three days now before finally admitting the circuit was no good.
I've learned a little bit. I am wanting to regulate the volts from a solar panel down to 12v so's it can feed directly into a tiny 12v pump. I'm happy to waste the excess and happy to avoid batteries and regulators.
The circuit i have is just a TIP122 is all. A cap across the input. And here's the thing: AI stipulated a 15v zener and a 1k R in series between collector and base. That's what we never could get working.
Seems from what I think I've learned that the R should be between collector and base and the zener between base and the neg rail which runs straight from source to load, the pump.
Is that right? And if so is 1k ohm for the resister about right and a 15V 1W zener?
It is a tiny 12v pump and the panel is supposedly a 12v panel but puts out up to 20v when its raging.
If there's a place to look up circuits like this I' like to know about it. I'd look them up.

How many amps does the circuit need to draw? An LM317 is easy to configure and can provide up to 1.5A of current.

 

A Darlington transistor such as the TIP122 in a regulator will have a minimum voltage drop of about 1.2V from input to output.
Is that okay for your needs?

That can be dropped to 100mV or less with a somewhat more complex (3 transistor) circuit.

How much current does the motor take?

 

I had issues with a neighbor's dog barking. Bought a 9 volt sonic egg that emitted ultrasonic sounds when detecting dog barking. Trouble is it was going off all the time when the Air Force flew by. Batteries would last 1 to 2 weeks before needing to be replaced. So I got a small solar panel and a buck converter and adjusted the output to 9V. That meant that during the day when dogs barked (or the AF flew over) it would work. When the sun went down it would not work. At night I figured dog barking could be a good thing. So that worked out quite well for me.

I bought this sort of buck converter:
https://www.amazon.com/DZS-Elec-Con...WGN1F6/ref=sxin_16_pa_sp_search_thematic_sspa
Still working today. And this was back in 2015. So 10 years and still reliable. It's cheap enough and no need to build anything. You get a small buck converter that can power a small motor - assuming your small motor doesn't draw more than 3 amps and your solar panel can deliver that much power.