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rufinus

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Posts posted by rufinus

  1. D10 was shorted.
    Many thanks goes to audioguru, the man, who cares.
    Respect.

    Now i wont connect ammeter between emitter of Q4 and output. I will better use voltmeter to measure across R7.
    I did build one based on 7107 and it works fine (as a panel meter for this project). Now i have one more, also based on 7107, configured for 200mV full range and with a voltage divider at the input to have full scale of 20.00v. I guess, i can use it as ammeter if i measure voltage drop across R7?

    Another issue is grounding. Here in Germany we have a grounding pins on the plugs. Should i connect the common of the psu to the ground, or just leave it floating and ground only the enclosure?

  2. With the load of 1 ohm voltage stays at 0, it can not be regulated. Current pot is in the middle. LED is off. 
    Voltage pot does not change anything. Current pot also does not change anything.
    There is no current regulation. Ammeter in the series with the load (1ohm) shows 0.03amps independent of current or voltage pot adjustment.
    Load resistor stays cold.

  3. With the load of 1 ohm voltage stays at 0, it can not be regulated. Current pot is in the middle. LED is off.
    With the load of 680 ohm voltage can be increased to 17.6v and then stops, but LED is still off. Current pot is in the middle.
    LED goes on only when current pot is completely down.
    Both loads are cold. It looks as there is no current basically  ???

  4. Hi audioguru. Thank you very much for your reply.
    Fuse is inserted straight after secondary winding before rectifier in order to protect the winding. It had a value of 2.5 amps and before everything was working excellent.
    I do have a 24v transformer and for building this psu i used your 24v mod parts list.
    So, do you suggest that D9 or U3 is dead?

  5. Finally i managed to put it all together. Everything was working fine. I connected 1 ohm resistor to the output and measured up to 2.5 amps through it. Voltage and current regulation was excellent. Then i decided to insert ammeter between emitter of Q4 and output, as audioguru suggested.
    And i got a blown fuse. After replacement, i can regulate the voltage. But with the same resistor connected voltage drops to 0 and does not regulate anymore. Current is something like 30 maA.  :(
    Any ideas??

  6. Yes, thank you, audioguru, but i already saw it. It is based on a chip from Atmel plus it is a surface mount version of chip, which will be difficult to mount for beginners. I work with PICs and program in PicBasic.
    There is no sourse code for development and in general schematics and project are not very clear, at least for me.

  7. Went for a walk and had an idea. Surely i want to have an volt/ammeter built in.
    Digital one. One way is to buy standard models such as 7021 based. I thought of making one myself. I have spare PIC16F870 which has four 10 bit A/D converters on board. And i just bougt two 2x16 LCD screens on ebay. The question is, how to make multimeter out of this. Software for conversion i can write, but how to interface 0-24 volts to 0-5 volts of PIC? Hardware is my weak point :(
    Besides simple multimeter it is possible to output other info on screen too, such as how mant watt load is consuming, temperatures of power transistors, control of the cooling fan... Any ideas will be appreciated. In the case of success i could share a firmware for PIC here on forum. If anyone interested....

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