Need help building backup

[engtech]

Hey guys. Newbie here. Just need some help building a backup. I've got a item that powers out with two AA batteries, i've got a solar panel that powers out 6v max.

question is. How can i make it so when i've got the solar panel running and i want the battery power to shut off and when the solar panel isnt supplying enough power, id want the battery power to turn on.

THANKS.

 

[Grossel]

The easy way to do this is by using two diodes. But then you'll loss a big part of the total power consumed.

Another easy (but not THAT easy) is to activate a relay each time the solar panel provide a certain voltage out. The backdraw here is that a relay consume much power compared to an average device powered by two AA batteries, and it's even not sure that the solar panel is capable to provide enough current for that.

Another way to do this is to use just one diode from the solar panel and just let the batteries stay connected all the time. But by doing this you must make sure that the batteries won't overcharges the batteries.

 

[engtech]

First. Thanks grossel for the info, this'll surely help me out.
second. Sorry for posting in the wrong section as to i'm a newbie.

Grossel. I'm currently been working with electronics but havent had much experiance with them. If you could imagine two AA batteries in a battery pack, and then I hook up a Solar panel with a diode, this means the solar panel is charging the batteries basically? am i correct? what kinda of diode should i use? If anybody else has any help, please let me know viewers out there. THANKS.

 

[engtech]

if i'm going to be charging the battery pack, which isnt such a bad project for me, id need a way for me to stop the solar panel from charging the battery at a certain charge point so they wont over charge and explode. My main help that i need is a way for the batteries to keep running. and when theirs enough light, the solar panel should turn the item on and the batteries to stop running.

 

[Grossel]

Which types of batteries is it?

I don't know how smart it is to connect a battery charging system (circuit) to a batteri that is already powering something else.

What equipment is connected to the batteries?

 

[engtech]

its connected to a Wireless Sensor Network, crossbow technologies. XM2100 antenna. its running with two AA batteries.

 

[engtech]

Hey Grossel. I'm actually trying to make it like this

1) the batteries are still connected, but when the solar power turns on, i want the battery power to disconnect fromt he device. This is the simplest i can get it down.

 

[Grossel]

Hey Grossel. I'm actually trying to make it like this

1) the batteries are still connected, but when the solar power turns on, i want the battery power to disconnect fromt he device. This is the simplest i can get it down.

No battery charging at all, no.

One more question: Is it cruicial that the voltage DOESN'T DROP when shifting from batteries to solar cell?

 

[engtech]

well..the voltage of the device is running at 3V obviously if 2AA batteries=1.5 volts a piece I guess as long as it doesnt drop below 3 volts its fine. Got any ideas grossel?

 

[Grossel]

well..the voltage of the device is running at 3V obviously if 2AA batteries=1.5 volts a piece I guess as long as it doesnt drop below 3 volts its fine. Got any ideas grossel?

No, that's no my question.

I mean, What happens if you touch the batteries so that power is lost for a second or so? Would that be critical for proper operation? It's a key question, because any solutions based on relays would cause such power drop.

 

[engtech]

Grossel. It won't matter if there is a power loss for a second. I understand where your coming from.

 

[engtech]

bump. anybody else wanna help? ill appreciate it. THANKS.

 

[electronist]

OK, lets start with what type of battery is being used : I mean Li-Ion or Cad etc.
What is your budget? Would you prefer buying chips or want to work somthing off the shelf?

A piece of advice: While everybody thinks of over charging you need to think of deep discharge cut off too. Or else your battery will sink too low.
Could you also specify the Current consumption of your circuit. You have written your Solar cell powers 6V but your battries are 1.5+1.5 = 3V. Have you got a regulator in place.
Give me more details and we can work out a solution

 

[engtech]

Hey there Electronist and Grossel. Thanks for submitting in to my thread. I'm a newbie with electronics but have been working with them here and there since i was a kid. i just need info on how i can make this piece work.

1) working with crossbow XM2110 antenna (Wireless Sensor Network)

2) runs on 2 AA BATTERIES

3) Want to make the device work so when the solar panel turns on, the battery side will turn off.

4) doesnt matter if there is a power drop.

5) dont have any parts yet to get this project started.

6) budget id say atleast below 80 dollars?, if there are chips involved, it might not be easy for me to work with them, unless there is some guidance.


anymore questions to make it easier for you to help me. feel free to ask.

 

[Mr RB]

I would use a 2.8v low quescent current regulator, and connect the solar panel to that, and a couple of NiCd or NiMH batteries in the battery holder.

 

[engtech]

Hey Mr. RB. Never heard of that part before. Would that help in setting up a way for me to want....

when the solar panel turns on, the battery power to shut off. Is that what this component will do?

THANKS, Thanks grossel and electronist for your help so far. i appreciate it. I cant believe they got this stuff in high school and im only a sophomore.

 

[electronist]

See if you can get a lead through this. We will discuss it in detail if you feel like

 

[engtech]

Hey electronist. The schematic drawing makes sense to me. If this will help me get my project started. I would need to know where to get the parts. I dont think radio shack would have any, besides the capacitors if those are what i see (1uf). If you want to name me the parts that are in there please, maybe i can copy and paste the image, and then write them down. then send them back to you. By the way, this class is really "learn on your own" which stinks to high heavens, i just dont get why my instructor cant help us, hes really a pain. I really appreciate your help so far, hopefully this schematic can get me running. THANKS.

 

[electronist]

Let the Diodes be 1N4148
If you are using battries use 3 instead of 2 else the regulator will not work.
Search for a 3V regulator on Google. Radio Shack should have all these components. Thy are really basic. The Capacitors are simple 0.1uF Ceramic to prevent ripples.

Remenber that the diode wil provide a forward voltage drop of 0.5V approx hence you need the battery to take care of this loss. Also any regulator will require almost voltage to be higher at the input.
Actually you can connect the battery directly to the load through the diode bypassing the Regulator. You will require the regulator only for the Solar Cell.

Does it make sense?

 

[engtech]

thanks electronist.

so if i get these parts, i can make the device work like this...

when the solar panel turns on, the batteries will turn off..therefore the solar panel is now powering the device?

the parts that i will need are

(2) 0.1 uf capacitors (what type of capacitors, i learned there are ceramic disks)

(1) 3.v regulator

(2) diodes (what do you mean by 1N4148?) is this the type?

(1) 6v solar cell

(1) 3.6v battery

(1) RL? whats that?

also, what does it mean by the three lines on the two capacitors, the RL...the battery and the solar side i know will attach to the device.

I wont have the ground, therefore can i leave this alone or attach it to the negative side of the battery?

THANKS.