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HI MrAl,
Sorry for late but we all were in the hospital. I have lost one of my nicest cousin she died few days ago.
So last night I was working on multisim for the circuit so having problem with lm317 components. It's not supplying desired current and voltage with given components values. I tried changing the value but still did not achieve the desired values. And I'm assuming that the power supply to whole circuit is 16v. Am I right?
Thanks
Waiting for your reply
16v sounds adequate yes. You only need a bit more than three cells in series plus 2v for the LM317 plus 1v for the upper transistor. So lets see, 4.2 times 3 is 12.6, plus 2v is 14.6, plus 1 equals 15.6 volts. That should work but if it doesnt try going up another volt.
Did you check the voltages at the pots? They all have to be adjusted right before using this thing. You have to have the voltages as indicated on the schematic or the unit may shut off because it thinks there is a fault.
Check the pot settings for the correct voltages. Then check the right side LM317 to make sure it can deliver the required current period by disconnecting from the rest of the circuit and drive it directly and use a small resistor as the load.
You must realize that sometimes you have to troubleshoot a new design a little bit but since this is so straightforward there shouldnt be too much of a problem. There's always the possibility that there is a wiring error too.
Im not sure if i mentioned this yet but the only IC's that can be comparators are the four (or five) that go to the LED's that connect to the 2N4403 transistor. The rest have to be op amps.
I just noticed one little detail that was not really correct. The caps on the LM317 go from the input to ground not from the input to the output. Check the updated schematic below and note the changes.
Hello MrAl,
last night i have completed circuit on my multisim software. it is working so fine that it start charging when any of the cell goes blew 2.7v and charge until it reaches 4.2v and it monitors individual cell. circuit is pretty Good. But one thing that the charging current from second lm317 is not going more that 6mA. i have tried different value of resistor on lm317 but current is not going more that 6mA. what could be the problem? or may it the wire connecting problem in Sim software?
It is too difficult to see the wiring near the right hand side LM317 you may have to take another screen shot or else check all the wiring there to make sure it is right.
R26 has to be about 12 ohms.
R1 should be 100 ohms and the pots need to be 500 ohms. If that is a problem we'll have to include some resistance to ground in that left side LM317 circuit.
The two transistors Q1 and Q2 are not oriented correctly. The emitters go "up" and the collectors "down".
Once you have those changes then check the collector of Q2 to make sure it is at least 15v when charging.
Because the charge current is so low (100ma as you say) you can use a smaller transistor for Q2 if you like.
Hello MrAl,
Sorry i did not check the orientation of the Transistors. but now i have oriented them in right way. and changed the values of resistor and checked the wiring But still the charging current is not going more than 6ma, even i made R26=12Ω and i tried making it 6Ω But current is not going above 6ma. and sim software is showing error on decreasing the value of R26 below like 200Ω. i can i only decrease the value of R26 when i make all the pots to their 100%. after taking all the pots to 100%, when i make R26=12Ω, the charging current is fine. multimeter show 100mA which fine But making all the pots to the 100%, fails the condition of those predefined voltage that to be supplies to the op-amps and comparators.
and today i went to the electronic shop. they are out of tip36. so can you please suggest me some other Transistor of same work please?
Yes 2N4403 just like the other one. This should work because the current is only 100ma.
If you cant get it to work we may have to do some careful testing experiments.
I told you you have to remove the connections from the right side LM317 and test it for 100ma. If you are sure it can put out 100ma then we can look at the other things.
The pots have to be set correctly but by design they were supposed to be 500 ohms each, so you may have to put a 1k in parallel with them to get the total resistance across the pot down to 500 ohms when they are adjusted in one direction.
You also have to set the pots starting from the one on the bottom and work your way up to the top pot.
If you still have trouble adjusting then we will change the pots circuit slightly to make it easier to adjust.
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she died few days ago.
