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Everything posted by MP

  1. MP


    The formula: HP = (V*I*Eff)/746)*5252 T= (HP /RPM) thus
  2. MP


    I don't think you have gotten any replies because this is pretty much a bogus question. Who could know how much tension is in the spring in this shade? You should contact the manufacturer or distributor and see if they have any torque specs. MP
  3. MP

    SPAM problem

    Blocking IPs would block people who did not spam as well. MP
  4. Not sure how much current you need from this, but you could use a capacitive divider in the same way you would use a resistive divider in a DC circuit. Two capacitors will divide the voltage and allow you to tap off at a lower voltage as needed. The formula is Vout = Vin*C1/(C1+C2) where C is in Farads. The voltage output is not dependent upon frequency, however, if the reactance of the capacitors is not large at the frequency of interest (i.e. capacitance value not large enough), the output current capability will be very low. MP
  5. Here is a timer circuit that will control a relay after a pre-determined interval. You can choose a time between 30 seconds and 24 hours. Hope that is what you are looking for. MP
  6. Arsal, You don't want to supply a voltage from the micro port to control a relay. Instead, use the micro to sink (drop) the line to 0 V. I use the Opto 22 Solid State Relays directly off the port pin of a micro for industrial control of mains with no problems. You don't need a transistor or any other components on the control circuitry of the SSR. Just your 5 volt VCC and set a high or low on the port pin. You can find what you need on their website at www.opto22.com Product literature, specs and pricing are on this site, but after you figure out which one you want, search for a better price in your web browser. Hope it helps. MP
  7. MP


    You are right on this point AG. The design with the two transistors circuit crossing each other is referred to, by many, as a "Flip Flop", but this is certainly an astable, not bistable and thus does not latch. Flip Flop was probably a poor choice of words. I think that the "multivibrator concept" in the post was clear in referring to this as an oscillator. I don't think I confused you, Onix, but if so, apologies. Square Wave Inverter design is always based on a simple principle of a 50 or 60 hz oscillator of some sort connected to a step-up transformer. MP
  8. Hey guys, This site is liable for copyright infringement. All those complaining are not the ones who will be in the worst of the legal trouble. Any one want to put together donations for a legal fund in case the site is sued? Yeah, I didn't think so! I think all mixos is asking, is that you do not post these books and magazines to the site. Just post a link to the site they came from or put them on a virtual hard drive and post a link to it. It's a simple concept. I would also like to point out that all of you agreed to this when you signed up to be members of this site. Do you also know that if the site was sued for copyright infringement, the lawyers would have access to your IP addresses and email addresses? Why rock the boat? MP
  9. MP


    Onix, The Inverter project is based on the multivibrator concept. This is also known as a Flip-Flop. In this case, a 2- transistor flip-flop. You can find many descriptions and discussions of flip-flops on the Internet. The output is a square wave. This design is not as stable as many more modern digital designs, but I have had other members report that the project worked without problems, too. One thing to watch for is that this type of flip-flop circuit can stall. In such a case, resetting power to it usually brings it back to life. Hope this answers your questions. NOTE TO ALL: I have moved discussion of operation of this project to the thread where this discussion was already started. I have also deleted some posts that are in violation with the member agreement and posts which related to them. Please keep posts civil and on track with the original post. You can always start a new thread if you do not want to keep your discussion on-topic with the original post. Hijacking someone else's thread to discuss a different subject usually ends in deleted or moved posts. MP
  10. Since this old thread was started, I have gotten feedback that others have built this Inverter. No one has reported to me that anything has burned or exploded. No injuries and no damaged devices connected to it. This could mean that Aaron's site has more newbies or people who should not be sitting behind a soldering iron, or it could be a number of other things. One thing that is very clear is that others have built this project and posts warning of injuries etc., are just rumor. Posts stating that the project will not work have also been proven wrong. I do not understand a member repeatedly posting scare posts on a project he has not built or had experience with, other than what he has read on the Internet. I think this subject is dead and should not be beaten into the ground further. However, I understand that this is not going to happen, so knock yourself out and complain all you want in this thread about this Inverter project. MP
  11. depends on the current needed and if the DC-DC converter can provide it. MP
  12. Casdale, Get a 5V fan that is rated within the current specs of the USB port. MP
  13. Hi Jeff, Welcome to the forum! My personal suggestion would be to buy him a soldering iron and a bread board kit. At this age, he will probably outgrow the snapkits very fast. For microcontrollers, you could start with the AVR line and a free Basic compiler named "Bascom AVR" from www.mcselec.com Bascom uses a language and IDE that is very close to the visual basic IDE. It will also give him familiarity with VB later on. The AVR can be programmed over and over again in the circuit it was designed in. This is a lot nicer than purchasing a programmer to burn the hex code into the micro. The trick to teaching micros to young students is to include displays, LEDs or sounds into a simple project. Good luck! MP
  14. Bat, It also depends upon which operating system you are using. Newer operating systems like XP are not as easy to do this for security reasons. I think someone posted a copy of Parallel Port Complete in the Resources forum of this site. Download it. It should cure your problem since it has snippets of sample code to accomplish what you are trying to do. MP
  15. You should post the model numbers in the data sheet request forum and/or the manual request forum. You might get a hit there. MP
  16. Yes, Radio Shack probably doesn't know there is more than one type of etchant in the world. What they carry is the ferric chloride. Also, if you plan to use lots, Circuit Specialists carries the powder form. Much cheaper to ship, but you have to be careful when mixing it with water or you can get hurt severely. Once mixed, it is the same as the bottled etchant you buy. MP
  17. Bob, Radio Shack carries Ferric Chloride. Also, you can order it through www.circuitspecialists.com MP
  18. The questions I posted are key questions to try and determine where the fault might be. Without answers to them, I really do not have a clue as to what is wrong. The pc power supply has quite a bit more amperage than what you need, but the power supply does not cause this problem. Something is drawing too much current. The power supply is only obliging with what is requested of it. You should find out what is causing the excessive current draw. My guess would be that you have designed a stepper board that requires more current than the UCN chip is capable of running through it. If this is the case, you should scrap the idea and build a controller board that is capable of a few amps or more. Perhaps you have chosen some wrong components that causes a draw. Can you post a drawing of your board? I tried to determine more from the pictures you posted, but they do not help for diagnostics. Post your board layout and description of parts you have used and we can try to determine if it is a component or too much current draw from the motors, etc. MP
  19. Skipper, Mixos is using this voltmeter for his 0-30V power supply. He states earlier in this thread that he uses 12K for R3 to get one decimal point precision on a 0 to 30 volt scale. His comments are here: http://www.electronics-lab.com/forum/index.php?topic=5629.msg636#msg636 There were a number of corrections made in this project at the beginning of this thread. However, the R3 resistor scaling was probably missed. There is also another project in the same directory that uses the same ICL7107 chip. It has a scaling switch. You can see that project here: http://www.electronics-lab.com/projects/test/007/index.html Perhaps it will also give you some ideas. Hope that helps. MP
  20. Nickolaw, What are the symptoms of the fault? When you say it is not working, what is it doing? Have you checked the power supply? Has something burned on the board? If not, have you checked all settings in the software? Have you slowed down the steps to make sure the motor is not stalled? Have you checked the pulses coming from the board? If you use a slow stepper setting, you can use LEDs to check the stepping sequences. This is a useful tool as long as you step the motors slow enough to see the individual steps with the LEDs. Don't forget to add resistors so that you do not burn out the LEDs. MP
  21. What did you use for R3? Also which pin 5 did you jumper on the display? MP
  22. I use 1% tolerance resistors for everything. R3 in this project must have such accuracy, but the others could be 5% if you have trouble getting 1% tolerance in your area. Ceramic caps are cheap, but they are not real good, either. If you use a higher grade material such as poly, mylar and tantalums, you will have better results. There is no problem using Electrolytic capacitors for the supply bypass lines. There might be some guidelines in the data sheet regarding this as well. This is not a big issue. If you use ceramic caps, the project will work. In fact, the Smart Kit probably uses the cheapest components off the shelf. This was only a suggestion to a better product. MP
  23. You will have to experiment a little on the capacitor size for the alternator noise. This is the same problem you might encounter with anything you build and add to your car. You might even need to use a choke and build an alternator noise filter if you have a lot of noise in your system. It will depend a lot on your car make, how old the alternator is, how worn out it is, etc. It is also possible that you will not even need to do anything at all. I would try no filtering at first and then add on to the design as needed. Ceramic capacitors? I would recommend that you use better capacitors. MP
  24. The chip does not have a high watt rating. If you are using steppers that consume large amounts of energy, you could damage the chip. What is the rating of your steppers? What is the rating of the power supply you used? MP
  25. Nef, If you did not set the fuse bits correctly, the micro is not going to work correctly. You need to re-program the PIC before you can do much else. MP
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