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Everything 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. Have a look. I was trying to use it with my 8051 microprocessor. If I replace 100K with a short, the circuit 1/2 works (receives correct data) and 1/2 the time, it shuts off, turns back on, and then resets. Would capacitors help? I already have everything on a PCB and do not wish to change the layout.
  4. as for the circuit MP believes to be correct, why are there so many transistors? why not just have two transistors? AND, why are there so little resistors? I think there should be some near the transistors. Its the resistors that limit current and prevent overheating.
  5. 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?
  6. I tried adding resistors, and making it more like talkingelectronics version, but that didn't help. At the moment, my input wires are about 6 inches long, because this section is in the beta stage, and my radio portion works. 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! 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?)
  7. 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?
  8. I haven't had a transistor blow up in this configuration. 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. then I must be on the right track. Because I don't want IC constraints to affect my design. I am going to search for that. Thank you.
  9. 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.
  10. 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.
  11. Audioguru stated: Indulis stated: The full post can be found at the following URL: http://www.electronics-lab.com/forum/index.php?topic=8320.0
  12. 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?
  13. most likely, no. The only way it might help is if a large value one was connected across the ppower supply to smooth out the power voltage, that way, the voltage will be more consistent as the power supply drains. other than that, I cannot see a capacitor as a helpful device.
  14. According to your past equations, It seems that my error rate is at about 6%. Maybe my luck is so bad now a days, that this error rate is making problems for me
  15. 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?
  16. I think so. I'm mainly using a DC adapter. Seldomly, I use batteries. I haven't measured it. but shouldn't the range of any homemade R-2R DAC go from 0 to full voltage? and what does voltage range got to do with continuous tuning?
  17. I used the 2N2222, because I wanted a common transistor that can give a higher range of capacitance when used as a varactor. 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.
  18. ;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?
  19. 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 ;)
  20. I tried again and this time it works. It must be the timing.
  21. I just bought a blacklight from Spencers. It is similar to the model at the following URL: http://www.spencersonline.com/index.cfm/fuseaction/products.detail/categoryID/4c03fc90-c45d-43ab-9664-11034dcbf79d/productID/30443747-4c20-40e7-8ed2-c81920107086/ 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.
  22. according to several documentations, they suggest between 20 and 30 minutes. 3 minutes is very short. I don't have those kind of lights. What I am using is a halogen light that is commonly available. so what you are claiming is that my current light source is almost useless. this isn't light work. I'm doing my own microcontroller circuit, and the spacing is tight (200um minimum). I already doubled my spacing since I started this thread. 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. What is the absolute maximum exposure time I should use?
  23. I was wondering if I used the transparency, pass it through once through the printer, and create a longer exposure time, would that make a notable difference? My exposure times are usually one hour, but if it is worth it, I am willing to up it to at least 3 or 4 hours.
  24. 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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