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Looking for a simple circuit for power regulation and led indicator light

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pityocamptes

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Power intake will be from solar and testing it yesterday showed power fluctuations from 5 volts dc .85 amps to 3.5 volts .4 amps. due to clouds or more important its a non tracking system. The charging circuit I am using uses a chip that is only good until 5.5 volts. Can someone suggest or post a simple circuit that limits voltage (with little waste) to 5.5 volts maximum and controls two leds (one red and one green) - the green led will stay lit if the voltage stays above 3 to 3.5 volts and switches red if the voltage drops below 3 or 3.5 volts (haven't decided on a ceiling or floor voltage). Thanks!! Looking for a low voltage circuit option as the solar panels and charging unit will basically be powering the circuit.
 
Hi.

You need a DC-DC converter that supports both lower and greater output voltage. One such circuit is a Cuk converter
Then you need a controller circuit that applies pulses with variable length to the Cuk converter.
 
Thanks. I do have a buck boost convertor. So I could use that. How would I control two led lights for green being lit when voltage is within specs and it changes to red when voltage drops below specs?
 
What you really need is to get the proper panel for your application. If you have a circuit that requires 5.5V minimum at its input, then the open-circuit voltage rating out of the panel should be about 10-12V!!!!. As you start drawing current out of the panel, the panel voltage will drop. It will drop to ~5V at the current where you are getting max power out of the panel (so called MPPT). A panel that puts out 10-12V open-circuit in bright sunlight will still put out more than 6V in subdued light.
 
OK. I will check into that. Basically the led indicators is for the batteries that the panel will be charging. Can someone suggest a simple, low current draw circuit that has a green led lit when battery voltage within specs, and then it switches to a red led when voltage drops below a specified amount? Thanks again!
 
Thanks! This is a great board. I have one other question. I am looking at this: **broken link removed**

Will this step down work as follows, lets say my output is 5.5 volts dc. However, my input can fluctuate between 9-15 volts. Even though my input fluctuates, will my output remain regulated at 5.5 volts? Thanks again!
 
Here are some previous postings on this topic. Toward the bottom of the thread, the circuit was modified for ~6V. Modifying it for any other voltage is simple. Adding a bi-color LED (red-green) would also be easy.

So does your schematic provide a low voltage/current usage? I see where some wanted to use a relay, I did not see that in your circuit, which is good. Also, what resistors would I need to look at for changing upper and lower thresholds? How would you incorporate a bicolor led? I'm not very good at circuits so any help would be appreciated. Thanks again.
 
After looking at the schematic I understand what the components are and how they connect. I am not sure how the 8 pin irf7204 connects to the circuit?
 
Sounds like you need two voltage detector circuits, one that trips at a lower voltage, and another that trips at a higher voltage? That is called a "window comparator", i.e. if Vin>Vupper, then light the Green LED, if Vin<Vlower, then light the Red LED. If Vlower<Vin<Vupper, then light no LEDs?
 
After looking at the schematic I understand what the components are and how they connect. I am not sure how the 8 pin irf7204 connects to the circuit?

Where is the IRF7204? You better post your existing circuit.
 
I really have no circuit yet. I've been looking around trying to find something that will work for me. Yes, I basically need something that will light a green led for lets say source voltages above 9 volts dc. If the source voltage drops below 9 volts then the green led turns off and a red led turns on.

Also, on the ebay regulator do you know if the output voltage remains static no matter if the input voltage swings a little? So for example I want a fixed output voltage at 5.5 volts but my source voltage may swing between 9 to 15 volts dc?

Thanks again I really appreciate it.
 
Here is an Over-Under circuit. It shows Red if the voltage is too high (runaway alternator), Green if the voltage is ok (in the middle), and Amber (mixture of Red and Green at the same time) if the voltage is too low. Look at the date when I created it...
 

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What is the minimum operating voltage? Also, anything a little simpler that you can think of? I really only need two leds for over and under voltage. Any help appreciated. Thanks.
 
You still need two comparators, either the dual LM358 in an 8pin DIP package, or two of the LM431s. Eliminating the Amber state will reduce the parts count by ~ four.

What are the trip point voltages? What is the range of the input voltage?
 
You still need two comparators, either the dual LM358 in an 8pin DIP package, or two of the LM431s. Eliminating the Amber state will reduce the parts count by ~ four.

What are the trip point voltages? What is the range of the input voltage?


Not really sure what the trip voltages are as I need to do some more testing on the power unit. Off the top of my head, I would think that source voltage will run between ~9 to 15 volts dc. The trip would be for the green led to stay lit for voltages over 9 volts and to switch to red for any voltage under 9 volts. Thanks!
 
I found this circuit. How would I change it so that green led was on for voltages above 12 volts, red for voltages under 9, and nothing for voltages inbetween? Thanks! Oh, also how would I calculate the resistor values in case I need to modify it? What does VR1 do?

**broken link removed**
 
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I found this circuit. How would I change it so that green led was on for voltages above 12 volts, red for voltages under 9, and nothing for voltages inbetween? Thanks! Oh, also how would I calculate the resistor values in case I need to modify it? What does VR1 do?

**broken link removed**

I looked at this circuit, and I cannot see how it is supposed to work. With the non-inverting input of the op-amp grounded, I cannot see how it ever does anything. I think the guy was smoking something?
 
Not really sure what the trip voltages are as I need to do some more testing on the power unit. Off the top of my head, I would think that source voltage will run between ~9 to 15 volts dc. The trip would be for the green led to stay lit for voltages over 9 volts and to switch to red for any voltage under 9 volts. Thanks!

If you just have one trip point (9V), then just use a 2-terminal bi-color LED, and a single comparator (LM431 or other). Or, with only one trip point, there is no reason to have Red and Green LEDs; just have a single Red or Green LED. If the LED is on, it means one thing; if it is off, it means the other (Binary=2states).

The window-comparator I showed earlier is Tertiary, it has three useful states (Red-Green-Amber or Red-Off-Green, Over-Ok-Under).
 
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