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Posts posted by mik3ca

  1. I don't get it.

    What I want to do is design an 8051 system with 2 JEDEC approved 32K EEPROM modules, and a JEDEC approved 8K SRAM.  I want to do it on a single sided board.

    It seems that the JEDEC approved standard, just does not work with my 80C51 chip.

    Can anyone tell me why the JEDEC standard assigns certain pins to certain addresses and data on the rom instead of having the data pins all on one side of the chip and other pins address?

    Membership for JEDEC costs at least $6000 and there is NO way I'm paying $6000 to find out this answer.

  2. It seems that I only get ANY result if the 100K is replaced with a lower value resistor (330 ohms and under).

    As for blowing the transistor, I don't think I broke it.

    For the processor, I don't think I broke it either.

    No matter what I do, the best I get is that 1/2 the data is received correctly, and sometimes the system resets itself and displays screwed-up results.

    Maybe I'll try 1K, but I don't know if it will work.

  3. It seems that the ONLY way one can make PCB's using an inkjet printer is if multiple copies of the image, perfectly aligned are placed on the board.

    It appears that printing on the transparency only ONCE does NOT work. I just tried it a few minutes ago on a canon bjc-1000 printer, and as soon as etching was 1/2 complete, I noticed a number of tracks were broken, so broken, that I couldn't even use solder to bridge the connection.

    The problem with me using multiple copies is the fact that my bloody printer is a GAMBLING MACHINE!

    1/2 the time, I can get it to print many copies in the same spot, and 1/2 the time, I can't, and when I can't, then my money goes out the window.

    I think I will need to buy a laser printer.

    and if I do, which is the BEST laser printer for the lowest price, and why?

  4. The circuit is missing a resistor across the PNP's base-emitter to turn it off. Try 100k.

    I tried adding resistors, and making it more like talkingelectronics version, but that didn't help.

    Maybe your input wires are not shielded and are picking up mains hum.

    At the moment, my input wires are about 6 inches long, because this section is in the beta stage, and my radio portion works.

    Yes, about 22ms. A very quick blink.

    I want to minimize holding time, in case I pick up sudden changes in the signal. In fact, I would like to pick up some white noise too!

    A 1N4148 has a clear case and light makes it behave like a photocell a little. Some 1N400x's have a black case and light won't affect it. Try it.

    Why would I need a photocell to detect a signal?
    Is there a way to avoid the need of a photocell? (or a diode that behaves like a photocell?)
  5. that was the circuit I was talking about.

    That circuit barely works for me IF the resistor value is low enough.
    Sometimes, when I use the diode, the LED just stays on bright, and never dims.

    So the RC circuit in parallel determine the holding time?

    What if I were to replace the diode with one that can handle more power like the 1N4007?

  6. Hi Mik3ca,
    Your circuit doesn't have a current-limiting resistor between the transistors. So when the PNP has a high input level then its collector current is unlimited and one or both transistors will blow up if the battery can supply enough current.

    I haven't had a transistor blow up in this configuration.

    I don't know why you have a filter capacitor. Usually a capacitor is used with a rectifier circuit to hold the highest level for a moment so you can clearly see it.

    Talkingelectronics.com uses a diode in place of my capacitor. I tried that configuration without much success. When the diode is connected this way, doesn't it create a varactor? Which means there is guaranteed capacitance.

    You are trying to make 1/10th of an LM3915 or LM3916 bargraph driver IC.

    then I must be on the right track.

    Why not use one

    Because I don't want IC constraints to affect my design.

    with the Half-Wave Peak Detector circuit...

    I am going to search for that. Thank you.
  7. I'm trying to make my own VU meter, and I only have partial success. What I would like is full LED from full volume. My LED doesn't dance to the music :(

    The input is a resistor (which varies the strength) and a capacitor in series. This capacitor is connected to any audio source directly.

    this circuit uses a 2N4403 PNP and a 2N2222 NPN. The last NPN is used to give the LED a boost.

    I think I am OK with choosing resistor values, but the capacitor values are trouble. If I choose them too high, then I will have to wait while they charge.

    How do I choose the correct capacitor values?

    I am interested in converting normal audible sounds into LED signals.


  8. I'm just wondering, what is the absolute minimum time one would take to etch a 10cm square board if most of it is etch-resisted by the circuit design, and the etch resist is fairly new, never heated, and the board just sits in the etching tank?

    why do I ask? because I rather let the etching work for me while I do other things than to waste 1/2 hour or more watching a board.

  9. what did Audioguru say that was correct that I said wasn't.

    Audioguru stated:
    That is how a switched-mode stepup power supply works, but it doesn't stepup the voltage very high. For a higher stepup, a transformer is used with this coil as its primary winding, then the secondary winding has many more turns.

    Indulis stated:

    This statement is 100% incorrect...

    The full post can be found at the following URL:


  10. After reading a post regarding an inductor and an oscilloscope, (somewhere in the project ideas section), It seemed that Audioguru attempted to answer the original poster's question, but then it seems that indulis made post(s) claiming that some or all of Audioguru's answers are wrong.

    I have found some information from Audioguru to be correct.

    however, It is always better to learn from someone that is knowledgeable with the subject.

    So I'm wondering, who is better to learn from and why?

  11. The CD4040 has a very low amount of output current. If the resistor values in your DAC are too low then the output voltage will be too low and then the varactors won't tune in wide enough frequency steps.

    oh boy, now I have to go and buy new value resistors.
    So this must mean that these resistors are hogging the current in such a way, that the outputs from the cmos chip are meaningless.  :(

    According to http://www.electronicproducts.com/ShowPage.asp?SECTION=3700&PRIMID=&FileName=sepana1.sep2003, they state there are two types of R-2R ladders. Current mode, and voltage mode. Which is better for my case and why?

  12. Did you use low capacitance 2N3904 or higher capacitance 2N4401 transistors as varactors?

    I used the 2N2222, because I wanted a common transistor that can give a higher range of capacitance when used as a varactor.

    Did the circuit tune stations properly when just a DC voltage was fed to Rvar1?

    Yes it does, provided that a minimum of 4K resistance is connected between the tap of the control and the varactor input. The control then is a 2M (2 megaohm) control.

    I was wondering if my R-2R DAC is supplying too much current.
    When I used 62K and 120K as my R-2R DAC resistors, it worked better, but I didn't like those numbers because they make timings larger, and I only want to wait milliseconds between each button press.
  13. ;D

    What I wanted was a radio where I can change the stations, not have it change stations itself.

    When I designed it on the circuit board, it worked perfectly.
    As soon as I placed it on a circuit board and added the digital station changer (basically a homemade R-2R DAC attached to a homemade poor-mans varactor which is then connected to the tank circuit.) , I seem to get better quality audio out, BUT the major problem is that the stations consistently change. (this is after the digital station changer has been added).

    In my R-2R DAC, I use 4.7K resistors and 10K resistors. I use the 4040 CMOS counter chip and I tied the lowest unusued bit to the RESET. The clock input is tied to +ve through a 62K resistor. I think the 62K resistor may be a problem.
    I connected a button from clock to ground, so every time I press the button, the station should change because the voltage will be different which will then make the capacitance of the varactor different. I tried tying a capacitor across the button, but that made no difference. I also tried increasing the power supply capacitor from 1nF to 4.7uF, and I still have no luck.

    Does anyone have any ideas to a solution?

  14. I'm gonna see what happens when I change the developer mix.

    Usually what I do is mix developer with water, and then when I am done with it, I store it in a container and reuse the same mix until I no longer can use it reliably. As i use more and more of the same container, the colour of the contents become darker. (lightish brown-green).

    As for the light, I have it about 1 foot away from the board and when I expose, I switch all other lights iff so that the rays from the blacklight are applied to the board. It looks nice in the dark anyway  ;)

  15. I just bought a blacklight from Spencers. It is similar to the model at the following URL:


    I used it to try to expose the board. Fortunately, it was a test board that is 1 cm square.

    I attempted to make a ridiculously simple PCB. I just did 5 vertical tracks with random spacing inbetween them. Then I expose the board to the new light for about 20 minutes. When I developed it, the results were not satisfactory. It seemed that 1/2 the lines were missing.

    I'm wondering, what is the BEST ratio of liquid developer to Water?

    Usually I do 20 parts water to 1 part developer, and I squirt more in if the photoresist doesn't disappear quick enough.

    Yes, I store developer in a squirt bottle.  ;D  Each squirt is about a tablespoon.

  16. wow, 1 hour is a long exposure time. I usually never expose for more than 3 minutes.

    according to several documentations, they suggest between 20 and 30 minutes. 3 minutes is very short.

    I use a light table that has 4 of the fluorescent "black lights" in it

    I don't have those kind of lights. What I am using is a halogen light that is commonly available.

    You do not need dark black transparencies.

    so what you are claiming is that my current light source is almost useless.

    On lighter work, you can use less exposure time.

    this isn't light work. I'm doing my own microcontroller circuit, and the spacing is tight (200um minimum).

    This is where the spacing becomes critical. You cannot get real tight artwork with transparencies that are not dark.

    I already doubled my spacing since I started this thread.

    Try the black light method...

    Where can I buy a light bulb that shines the "black light" you mention? It would be nice if I could buy it like an ordinary light bulb, rather than buy the whole light box, which is probably not available to me anyway.

    and make some time tests on the same board using a black piece of cardboard to cover the board. Expose a small area for 1 minute, then expose same area plus another section for 1 minute, then uncover another area and expose again for 1 minute, etc. This will give you 1 minute, 2 minute, 3 minute, etc. exposures. Then when you develop the board, you can find your best exposure time. You might want to switch to a better photo resist and developer.

    What is the absolute maximum exposure time I should use?
  17. almost fine.

    I chose to increase the spacing since I am opting for cheaper medium.

    The circuit will print perfectly, but not dark (or solid) enough to make a practical PCB if I use a transparency.

    I have a standard blank sheet of printing paper, but I don't know if that will work because it is a notch more opaque than the tissue paper I'm trying to use.

    The tissue paper was bought from a dollar store which might be a problem.

    When I print on it, it seems that some tracks are connected when they shouldn't be. I bet tissue paper can't isolate ink well.

    Can anyone suggest a better medium? I went through tissue paper and transparencies without success.

    transparencies happen to be expensive ($1.70 / sheet)
    tissue paper on the other hand is cheaper for me ($1.00 / book of 40)

    I also want a medium that can absorb ink well.

    any suggestions?

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