Hi,
First post here. I have been reading books and made some simple designs. I am trying to make a circuit that has 4 flashing leds that connect to a solar panel that puts out 6v. And rechargeable 4 aaa bI can tteries. I have watched videos and designs on how this is do have. I havcuit e tried many of them and I can't not get them to work. Here is what I am using.

Pnp transistor
Photo cell
4 3v flashing leds
And resistors
6v solar panel
3aaa batteries

The auto dark circuit is driving me crazy. Every time I set it up its backwards. It lights up in light and off at dark. I need it the other way around. Also I can only get 1 led to light up. alot of times I can not even get the photocell to even work. This looks like a simple circuit to make and I can not get it. Any help or Info would be greatly appreciated!

 

hi Mm,
Do you have a circuit diagram that you could post.?
E

 

If you want to make your own circuit, carry on, but if you just want to get it done, go find a solar landscape light. They are cheap and sometimes free, and contain the exact functions you need. Then replace the LED with your flashing LED, and the solar panel with your (larger?) panel.

 

I have tried the solar lights already. Used my bigger panel and switched leds. I think it is to much power for that dark circuit to run it.

This is the diagram i am trying to use with 4 Flashing leds instead of the white.

http://www.instructables.com/id/DIY-solar-rechareable-automatic-night-light-outsi/

 

http://www.instructables.com/id/DIY-solar-rechareable-automatic-night-light-outsi/step2/schematics/

diagrams

 

Your transistor is an NPN, and will turn on when the light level gets to 0.7V darkness, a better circuit woul be to use a darlington, or an op amp.

 

Is there a reason why it is on when its light off when its dark?

 

Is there a reason why it is on when its light off when its dark?

hi Mm,
Check that you do not have the 2N3904 Emitter/Collector leads crossed over.

Do you have a photo of your layout we could see.?

E.

 

Photocell working in this picture its just backwards on with light off with dark.

 

hi Mm,
Are the two White leads the solar panel.?

If yes, it looks as though you have the _ve of the battery connected in series with panel.??

For a test, remove the White panel leads.
Connect the Black wire from your battery to the Emitter and the bottom end of the LDR as shown in the link circuit diagram.

E

 

I just added a better picture for you. the photocell is working but its reverse. I need the lights on at night and off during the day. I do not have the solar panel hooked up yet. I am trying to get this circuit right first. that white wire is just going from the ground of the batteries to the pnp and photoresistor

 

Hello,

When you want to reverse the action, exchange the Photocell and the resistor on the base.

Bertus

 

here it is connected wrong?

 

Hello,

Have a look at the circuit in this PDF:
http://educypedia.karadimov.info/library/ck1602.pdf

Bertus

 

Thanks Bertus i have the Photocell actually working now. Thanks for the file as well. Everyone helped me a lot with the first problem.

 

Batteries look like 4 AA, Ni-MH @ about 2500 mAh, so on full charge should last about 30 h, so you may avoid problem of over discharge if solar panel can keep up. Use a shottky diode between SP & battery as you need every V available from SP.
As PNP version is in storage , might as well post it.

 

Thank you!

 

You don't need both an LDR and a solar cell to do what you want.

The solar cell can turn on a PNP transistor when its voltage goes low. Run a diode from the base to the battery to charge it and keep the battery voltage from influencing the PNP transistor.

You can get the chip for solar cell garden lights here: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=131139182802

The chip does everything for you. All you need is a coil and LED's

 

I am trying this circuit out as well. I think I can use this 555 timer to make the leds flash , Solar, Charge batteries, and turn on at night. Can someone tell me where i would hook up the photocell to make this turn on at night? and will it work for me instead of the other circuit in this post? This way i can adjust the flashing to my liking if i go with the 555.