| Electronics > Projects, Designs, and Technical Stuff |
| Bench CC/CV PSU Based on Daves uSupply (Not Anymore) |
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| iMo:
The current limit LED indication - the output of the CC opamp - the I_Sense - will drop from aprox +V to -1V during the limit. You can wire an LED from opamp's I_sense output against the +V through a resistor, say 15k, and it will lit during the CC limit. |
| Kleinstein:
For current limit the OP for the current loop will no necessary go down all the way. With a resistive or similar load that is just a little high the voltage would only drop a little. The usual way to check is to compare the outputs of OP1A and OP1B, e.g. with another OP/comparator. Just an LED to V+ may not light and could be rather dim if the voltage is still rather high. |
| KC0PPH:
Once again thanks for all the feedback. I incorporated everything that was mentioned about the schematic.Sorry about the last version of the schematic. For some reason a lot of things did not render correctly like V+ showing as V-. A few notes. Q1 (Pass Element) is listed as a TIP41C but it will be a TIP120. I did not have a model for the TIP120 in a vertical position and did not want to make one. For the Board layout - I will try a bit harder in my layout to keep traces short. I will also try and keep one side of the board as solid GND. I did do a fill on top/bottom with GND. I need to figure out how to add vias without traces but will stich them together. I put in a 431 Reference as suggested and I have a few of those laying around. I added a 10uF bypass cap per the datasheet recommendation. Well it did not give a value so I picked 10uF. I will eventually be using 0-4.096 as my analog values coming from my microproc so for now I will scale everything to 0-5V. I set up an OA with Gain of 2 to accomplish this. I think i most likely screwed everything up but here it goes: The current sense resistor has changed to a single 1 ohm resistor. I still have the 2 standard 1/4W ones in the schematic, but I will just solder in a single 1Ohm 50W resistor. From that decision I then calculated resistor values for the inverting input of IC1B (Current Sense Amp). I wanted to turn 0-15V into 0-5V and so I used a 51K and 25K resistor network. For the inverting input I will have 14V with 1A Load. I believe someone said you want to keep your resistor values the same so I did. This means that in order to keep the OA happy I need to supply 0-1V on my ISET to get 0-1A. To accomplish this my Pot has changed from a 50K to 5K and there is a series resistor of 20K which should give me 0-1V. For the voltage sense I kept the same resistor values to scale the 15V to 5V. Since my reference is 5V I am going to short out that resistor on the pot (Listed as 0Ohm for now) The 50K pot should then give me 0-5V. P.S. I know you guys are only trying to be helpful but on my calculations please dont correct them "when" you determine they are wrong. I would like to try and figure these out myself so when I go to the uC version Ill understand how to modify the circuit. |
| KC0PPH:
Ignore the OA Power pins.... |O |
| KC0PPH:
BTW Ill be ordering 10 of these boards so everyone who is helping out is more than welcome to one. Just give me a shipping address once I place the order and ill ship em out. |
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