Timeline for Double Li-ion charging circuit logic
Current License: CC BY-SA 3.0
9 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Aug 18, 2014 at 19:47 | vote | accept | Alex Freeman | ||
| Aug 13, 2014 at 4:20 | comment | added | Russell McMahon♦ | @AlexFreeman - You can give a non-inverting gate or string of gates hysteresis by adding a feedback resistor as per my diagram AND a series input resistor to drive them. That would work for IC1 IC2 in my cct and the latch will probably work OK with ordinary gates. The delays on OC4 and IC5 will work without a Schmitt but the output transitions will be "soggy". If you add a 2nd inverting gate back to the input with a resistor from its output to the original input you get positive feedback = hysteresis. | |
| Aug 12, 2014 at 21:44 | comment | added | Alex Freeman | Right, okay. I had a look at schmitt inverters... They're a lot more costly than non-schmitt. Is there any way I could use positive feedback to give it hysteresis? Failing that, I believe comparators have some inbuilt hysteresis; would these perhaps work in a different way? I've already spent enough on NAND gates, so I was hoping that I wouldn't have to buy anything more. Nothing against schmitt inverters as such, I just thought that I might easily be able to work with what I've got. | |
| Aug 12, 2014 at 13:14 | comment | added | Russell McMahon♦ | @AlexFreeman - Understood BUT the only part you do not have is the hex Schmitt inverters, they cost very little, they come in little time, they use far less parts for this and other tasks AND once you realise what you can do with them they are your friend for life. | bout 30c to 40c each in 10's at Digikey. | |
| Aug 11, 2014 at 22:52 | comment | added | Alex Freeman | Right, but, I'd rather work with the components I have, rather than buying new ones if i can avoid it. I currently have a bunch of comparators, amplifiers, NAND gates, and of course all necessary passive components. I'm trying to build this as soon as possible so i'd rather not order in anything if i can build it with what I have here. | |
| Aug 11, 2014 at 21:53 | comment | added | Russell McMahon♦ | @AlexFreeman .... make the delays asymmetric - Caps charge positively slowly and discharge rapidly. This gives the non overlap function as when one gate turns off it does so soon after transition while the matching turn on is delayed. The hysteresis stops these signals being a soggy mess. | The Schmitt gates can also act as an oscillator (1 gate), PWM converter or audio amplifier (!!!) 1 gate, much more .... . | |
| Aug 11, 2014 at 21:49 | comment | added | Russell McMahon♦ | @AlexFreeman You can use comparators BUT the gates use less components, probably cost less and, once you see what can be done with them, provide you with decades of new solutions :-). | IC1+2 form a latch because they have zero inversion end to end and Rl provides positive feedback. Any input that can overcome Rl feedback controls the latch - here /CHG or pushbutton. A cheaper simpler latch is hard to come by. | Hysteresis turns the gradual analog transitions into sharp digital edges. IC4 and IC5 provide sharp on/off gate drive signals derived from the RC delays. The Rtx diodes .... | |
| Aug 11, 2014 at 21:43 | comment | added | Alex Freeman | Right, very nice. This looks very much feasible. A few things though: -Can I use a comparator with feedback to make the schmitt inverters? -Why do the inverters need hysteresis? -Can IC1 and IC2 be replaced with anything? A dual inverter seems a little redundant to me. | |
| Aug 11, 2014 at 11:14 | history | answered | Russell McMahon♦ | CC BY-SA 3.0 |