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LM317 digital control
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ZeTeX:
I really recommend you to build the circuit in ltspice and test test your control loop, I bet it will oscillate a lot.
just wondering, how are you limiting the current? I don't know a lot about logic gates so as and interest I would like to understand what exactly are you pulling down to limit the current.
(I might be wrong but it seems like the relay you are switching on with Q1 does nothing?)

Maobuff:

--- Quote from: ZeTeX on May 22, 2016, 12:35:52 pm ---just wondering, how are you limiting the current? I don't know a lot about logic gates so as and interest I would like to understand what exactly are you pulling down to limit the current.
(I might be wrong but it seems like the relay you are switching on with Q1 does nothing?)

--- End quote ---
R1-10 are current sense resistors, IC2A is diff amp that give voltage proportional to current (1V=1A), IC2B is comparator which compare voltage drop in those resistors and set one by DAC. If powered circuit consume more current that was set  output of IC2B is high, which feed in CLK pin of flipflop. When CLK changes from LOW to HIGH value from D is pushed in to Q. Than its turning on transistor and relay disconect reguator. To turn on back relay, i need reset flipflop(basically put LOW on to CLP). Swtch part of relay is K1 near LM317.
Maobuff:

--- Quote from: Kleinstein on May 22, 2016, 09:03:29 am ---The analog part has a few problems: the OP does not like a 100 nF cap at it's output. So some additions are needed here, to alow the OP to drive such a capacitive load.

Turning of the supply to the regulator in case of over-current is risky. A inductive load might give quite some kickback and thus damage the regulator. So there should be some over-voltage protection, at least a diode from the input to main filter cap.

The way the current is measured is also not that great: the resistive divider introduces quite some error and reduces the already small voltage at the shunt. So errors are rather large.  To prevent the overcurrent turn off part to activate directly when turning it on, there likely need some filtering caps / delay. With a relay you also need to have this part to be latching - otherwise the relay will immediately turn on again.

The µC might need a crystal to reliably work with the UART. With some tweaking it works without if the temperature range is not to large. The 2 DACs would need separate latching / CS signals to give different outputs.

--- End quote ---
Chip select pins are separate, one have IC name and other is VC. And yea its mine mistake to join latch of both dacs together. i know about current measuring error. I can minimize it by using 0.1% resistors. I will add crystal to my design. I will reduce or remove cap from adj pin of LM317, Thanks.
ZeTeX:

--- Quote from: Maobuff on May 22, 2016, 01:49:49 pm ---
--- Quote from: ZeTeX on May 22, 2016, 12:35:52 pm ---just wondering, how are you limiting the current? I don't know a lot about logic gates so as and interest I would like to understand what exactly are you pulling down to limit the current.
(I might be wrong but it seems like the relay you are switching on with Q1 does nothing?)

--- End quote ---
R1-10 are current sense resistors, IC2A is diff amp that give voltage proportional to current (1V=1A), IC2B is comparator which compare voltage drop in those resistors and set one by DAC. If powered circuit consume more current that was set  output of IC2B is high, which feed in CLK pin of flipflop. When CLK changes from LOW to HIGH value from D is pushed in to Q. Than its turning on transistor and relay disconect reguator. To turn on back relay, i need reset flipflop(basically put LOW on to CLP). Swtch part of relay is K1 near LM317.

--- End quote ---
So basically you just disconnect the power to the LM317? I dont think it is that good, the caps need to discharge and the regulator need to turn on \ off if you have something that gets current limited in a very fast pulses. I will test it in ltspice
Maobuff:

--- Quote from: Kleinstein on May 22, 2016, 09:03:29 am ---Turning of the supply to the regulator in case of over-current is risky. A inductive load might give quite some kickback and thus damage the regulator. So there should be some over-voltage protection, at least a diode from the input to main filter cap.

--- End quote ---
Can i move relay to output of supply?


--- Quote from: ZeTeX on May 22, 2016, 02:02:23 pm ---So basically you just disconnect the power to the LM317? I dont think it is that good, the caps need to discharge and the regulator need to turn on \ off if you have something that gets current limited in a very fast pulses. I will test it in ltspice

--- End quote ---
Yes, that why im thinking of moving relay to output
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