R4 needs to be reduced to increase the brightness of the LED when two batteries are being charged.
With only one battery ( 1.2V) there will never be enough voltage to switch on a LED which will need more then 1.7V (special type) or 2.2 V general purpose type.
Frank
LED1 is "stupid" and simply lights when the circuit is powered and its output is not shorted. LED2 lights all the time the circuit is powered and even lights if the output is shorted.
The LED does not only light when the battery is fully charged.
RV1 adjusts the maximum output voltage. One fully charged Ni-MH cell is 1.35V if charged from a low current and is 1.5V when charged from a high current. I charged my Ni-MH cells 2 weeks ago to 1.45V and today without a load they all measure 1.35V.
A Ni-MH battery charger IC detects the slight rise then drop in voltage that occurs when a cell becomes fully charged then shuts of the charging and turns on the LED that indicates the charging is finished.
Here is a graph of the voltage of a Ni-MH cell being charged a various currents. See the slight rise then drop in voltage when it becomes fully charged:
R4 needs to be reduced to increase the brightness of the LED when two batteries are being charged.
With only one battery ( 1.2V) there will never be enough voltage to switch on a LED which will need more then 1.7V (special type) or 2.2 V general purpose type.
Frank
Actually, after pass through the LM317T, the output for LED1 around 2.5V, but after assembly the battery, the voltage across LED1 become 0, and the open circuit part of battery is around 3.5V...
RV1 adjusts the maximum output voltage. The values shown result in a minimum of 4.79V when RV1 is shorted and the maximum voltage is 8.63V.
The voltage across LED1 will never be 0V because the minimum output of an LM317 is 1.25V.
RV1 adjusts the maximum output voltage. The values shown result in a minimum of 4.79V when RV1 is shorted and the maximum voltage is 8.63V.
The voltage across LED1 will never be 0V because the minimum output of an LM317 is 1.25V.
Audioguru, look at this thread https://www.edaboard.com/threads/336229/
I advised tengyy to replace the 0.5 ohm with a link, if he did that then he will get 0V on the LED when the cell is s/c.
Do you want CV mode to turn on LED or when CV mode drops to below 10% current?
If so ,then detect that with a comparator across Rcl with threshold =0.07V and use open collector to shunt LED2 via a smaller equivalent R value. Swap LED colours so Green is on output and thus 3.3V/6.6mA= ~470 Ohm or less. between open collector and LED2 Anode.(+)