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Herman the German

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Posts posted by Herman the German

  2. Timer

    in Electronic Projects Design/Ideas

    Posted


    You can Also build it with just a Microcontroller very simple and with lots of abilities.
    Of course building such circuits with TTL Ics is much more enjoyable.

    HTH - Shahriar


    A very good idea. maybe I can handle the hardware but not the software. The other way with wired logic is easy to understand and also easy to trace in case of malfunctions. I have made a lot of control units for industrial purposes, but never used a Microcontroller. Wired logic is just my thing! Even using a full size 19" rack with up to 17 PCBs  doesn't bother me at all.  Boole's algebra is logic. A small piece of (SMD mounted plastic or ceramic) is not logic and will become as intelligent as the programmer is.

    sincerely

    HtG

  4. cpu cooler

    in Electronic Projects Design/Ideas

    Posted

    ;)Peltier elements are not the right thing to cool a CPU. If You want excellent cooling You must use a water cooling system similar to engine coolers in cars. They are available in many electronic shops in Germany. Try CONRAD.DE. Of course they are very expensive too because of all the safety precautions not to flood Your PC.

    Peltier elements can produce 60 degrees of temperature difference between both sides. They take a lot of energy and do not only produce cold but also very hot sides of the module. To get rid of the heat You will have to employ a big fan and a very big heatsink. A small element is normally rated 2,5A at 12 to 14 Volts. And this element is NOT enough for a (overclocked?) CPU.

    Regards

    HTG (Herman the German)

  6. Constant current source for a low Ohm load

    in Electronic Projects Design/Ideas

    Posted


    How would I go about creating a constant current source to supply a 20 Ohm load? I want the current to be variable from 0 to 120 mA.

    So I need a circuit which supplies a constant current to a 20 Ohm load, in the range of 0 to 120 mA.



    ^ That is a circuit that I have designed already, however I believe it is a little unstable and the transistor may need a heatsink to suffice the circuit.

    I was hoping that perhaps there is a way to achieve a circuit that is independent of temperature, so I won't need a heatsink or have to worry about possible thermal runaway.


    Please check at ELV.DE. As far as I know they offer a programmable current sink for a widespread band of operation. Don't sink too much current - otherwise You will have to buy an own nuclear power plant to cool the device properly.

    The german word for this device is: Programmierbare Stromsenke

    Regards

    Herman the German

  7. UV exposure box

    in Electronic Projects Design/Ideas

    Posted

    Yes, I can do!

    The film or whatever You use to expose Your future board likes parallel light very much and the more even the light is distributed over the entire board area the better will be the result. I built a box when I lived in germany (now Thailand, the no-have country) I used 6 fluorescent lamps Type TL29D16/09N and kept the spaces closer than 1 inch. Before I built the box I metered the light and gaps greater than 1 inch are absolutely the worst You can do to Your box.

    15mm (1inch=25.4mm) is the best to do. You have the light almost parallel and enough room between the glas tubes for cooling. UV-A produces more heat than white light. If You use aluminum foil on the bottom of the box (not straight and even, just a little bit crunched) You will increase the reflections but don't do too much of crunching because reflections will penetrate the film slanted and that means unwanted exposure. Check the film side at the photoresist, closest contact. Printing on the wrong side has to be avoided under any circumstances.

    Have a good time building Your box.

    Best regards

    Herman the German

    P.S. I am about to build my box soon but this one will almost be unafordable in EUROPE since I will make it from Teak-wood (only used on ships and extravagant furniture)

  8. PCB photofabrication

    in Electronic Projects Design/Ideas

    Posted

    Here is another suggestion but I am sure it will work with Your system as well as it works with mine.

    I am using EAGLE and for best printing results I use the solder and the component side (solder side is blue and component side is red). On the screen they look violet but on the paper they are just black.

    That means to make an extra copy of Your layout just for printing purposes. Copy all traces onto the component side and the print will be deep black (as black as a road tunnel at night) printing both layers at one time. There will be no loss of the sharpness conerning traces, pads and vias. There is a good chance to fill unwanted holes on the solder side with colour on the component side.

    I tried this also on a colour laser and very much to my surprise there was no significant difference.

    For the developer I use "Aetznatron". Sorry I don't know the english word for that but the development is finished within 30 seconds. Any longer development will also erase the photoresist not exposed to light and You'll have a clean copper surface. The solution is 10grams per one liter of lukewarm water. 30 degrees will just be fine. Don't use higher temperatures. The result is unpredictable.

  10. Timer

    in Electronic Projects Design/Ideas

    Posted

    Hello everybody,

    one of the forum members gave me this forums name to become a member. He thinks it will be helpfull for some of You having difficulties putting together an electronic device of a german kit concerning the language. I will be glad to help everybody out with translations and if necessary illustrations.

    Just let me introduce to You briefly. I am Hans, a retired GAF captain, having flown all kinds of aircraft for 23 years, last RF4-E Phantom. Since I handled my aircraft allright it always handled me right and I had no accident during my flying time.

    I have a problem concerning a timer schematic. That is what it is supposed to do:

    Count up and down, must be presettable for up and down count and stop counting after the preset time has elapsed thereby triggering a sound signal and a relay. I've got the schematic so far to count up using  M74HC190 and the appropriate BDC to 7-segment decoder and LED driver but I have no idea about the "count down" part and how to switch back and forth. May be somebody has the circuit in his drawer and can help me.

    Thank You all for Your attention

    Kind regards

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