conntaxman
- Jun 17, 2011
- 89
- Joined
- Jun 17, 2011
- Messages
- 89
lm317
TB. you made me smile, thats what I need,isnt that about the same as the last pic i put up? ok let me explain what I want to do.
I put a flag up and at night you are suppose to have a light shine on the flag,[respect to the flag]or you should take the flag down.
I make the solar panels,out of 3x6 solar cells which give off 1/2 volt dc and max 3amp.So ill make a 6 volt panel useing 12 cells that will give 6volts x 3 amps.
I figure that i would use 2 of those 3.2 volt x 1000mah batteries. Just in case I want to add more leds. Now the leds are the reg 10mm whith in volt 3 ,current draw is 20ma .Now the amount of light per day im going to say about 7 hr.So i know their will be enough of sun to charge the batteries,I know on cloudy day you dont get much light. Want to LEDs to turn on at dark and trun off in the morring. so we have about 15 hr of draw on the batteries.I looking in the winter when it gets dark around 4am ,light about 7am.
So your drawing is what I want,or trying to make. Oh, the Solar cells don't produce any electricity at dark. So on your drawing i wouldnt need Q1 R3 R2 would i.You have those to turn off the solar cells, or is that used for the current to the batteries.
I thought to charge a battery you have to have the voltage a little Above the battery voltage to charge it fully.Like a car battery its 12, but you need about 18 volts to fully charge it up.
oh the current from the solar panel will most likely fluxuate a bit.
Is the last drawing i made right? I just need to know the val or R6 ,to me thats confuseing to figure out.
tks
John
Conntaxman,
Let's throw out the schematic for a minute. I want an extremely detailed description of what you want to accomplish with this circuit. How many hours a day is the solar panel going to be in the sun? What is the maximum current available from the solar panel? What is the average current that is going to be available during normal operation? When do you want the LEDS to be on? Only during the night? Let's say you want 24 hours of light from the LEDs. 24 hours x 2 LEDs x 20mA each gives us 960mAh. This means that you could run your batteries in series and still have enough capacity. What is the Vf of your LEDs? Is it less than 3.2V? Are you only going to want two LEDs? Or will you want more? Depending on the problem, sometimes it's better to start from scratch than to try to modify a design you're only going to use a small part of.
Let's say you want to charge the batteries at 4 volts and 200mA. This means the cells will be charged in approximately 10 hours.
Here's what I came up with. It may be right, or it could be wrong. I'll let someone more knowledgeable than myself chime in.
12 volts comes in from the solar cell. It passes through D1, then the LM317, where it's regulated to about 4.7 volts. At this point, an LDR (light-dependent resistor) and NPN transistor ground out the ADJ pin of the LM317 when it is dark outside, cutting off charging. Diode D2 prevents the batteries from discharging into anything except the LEDs. A second LDR and NPN transistor turn on the LEDs when there is insufficient light shining on the LDR. You'll need to figure out the value of R8 and R9 according to the Vf of your LEDs.
I chose R4 and R5 like this: Approximate charging voltage is 4 volts. Battery voltage is approximately 3.2 volts. 4-3.2 = 0.8 volts. Charging current of 200 mA = 0.2 A. V = I*R. 0.8 / 0.2 = 4. Round up to the E12 value of 4.7 ohms.
Let me know what you think.
TB. you made me smile, thats what I need,isnt that about the same as the last pic i put up? ok let me explain what I want to do.
I put a flag up and at night you are suppose to have a light shine on the flag,[respect to the flag]or you should take the flag down.
I make the solar panels,out of 3x6 solar cells which give off 1/2 volt dc and max 3amp.So ill make a 6 volt panel useing 12 cells that will give 6volts x 3 amps.
I figure that i would use 2 of those 3.2 volt x 1000mah batteries. Just in case I want to add more leds. Now the leds are the reg 10mm whith in volt 3 ,current draw is 20ma .Now the amount of light per day im going to say about 7 hr.So i know their will be enough of sun to charge the batteries,I know on cloudy day you dont get much light. Want to LEDs to turn on at dark and trun off in the morring. so we have about 15 hr of draw on the batteries.I looking in the winter when it gets dark around 4am ,light about 7am.
So your drawing is what I want,or trying to make. Oh, the Solar cells don't produce any electricity at dark. So on your drawing i wouldnt need Q1 R3 R2 would i.You have those to turn off the solar cells, or is that used for the current to the batteries.
I thought to charge a battery you have to have the voltage a little Above the battery voltage to charge it fully.Like a car battery its 12, but you need about 18 volts to fully charge it up.
oh the current from the solar panel will most likely fluxuate a bit.
Is the last drawing i made right? I just need to know the val or R6 ,to me thats confuseing to figure out.
tks
John