Here's what I'm trying to do.
I'm trying to make it where I can run any circuit requiring 5 volts off of 7.2 volts. I get 7.2 volts from combining two 3.6v ni-cd phone batteries but for simplicity I show it as one center battery in my circuit.
The source power shows as a battery but I plan to use a wall adapter that outputs either 9VDC or 12VDC, but I figure 9VDC is more efficient.
The battery shown on the right is the output (5V). I could replace it with an LED and resistor in series but I used a battery symbol for simplicity.
Here are my questions:
If I used such a circuit, would I be able to successfully charge a ni-cd battery to max charge without blowing up the battery or is my circuit flawed?
If my circuit can be successful, is there a way to modify my circuit so that I can connect a wire to a GPIO pin of an AT89C2051 so that it can detect when a battery is charged/still charging without negatively affecting the charging process.
- Could I change the variable voltage regulator (LM317) to an 8V fixed voltage regulator to charge the 7.2V battery with a resistor in series? If so, what resistor value?
I'm asking all this because I want to make a low-priced in-circuit battery charger for my microcontroller projects and I don't want to have to remove the battery in order to charge it.
Why this question isn't duplicate
I want to build the charger circuit using discrete components that are commonly available in anyone's junk box. I don't want to have to purchase a special IC and wait weeks for it just in order to charge batteries. Additionally, I'm looking for a modification to this circuit to make my charger more efficient. I adapted parts of it from talkingelectronics.com.