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Everything posted by jpknhtp

  1. Good point. Let it be known that for my last post negative doesn't refer to a negative voltage but rather ground. Anywhere negative is mentioned I mean when connected to ground 0v potential.
  2. I don't have the time right now to go into everything you need to know but here's what I can tell you. Transistors are current operated not voltage. A NPN transistor needs a positive current to turn on and the load goes between + Supply and the collector of the transistor. The base is where you put the control signal and the emitter goes to ground. A PNP transistor turns off with a positive voltage and must have the base pin grounded to "Turn On". With NPN and PNP the emitter and collector pins are reversed (Kinda). On a PNP transistor the + supply goes to the emitter and the load goes between the collector and ground. Edit: This may help you to remember The middle letter tells you whether the base needs a "N"egative or "P"ositive nPn= Positive base current turns this on pNp=Negative (GND) turns this on Also to know whether the transistor you selected will work for your application you must consult that datasheet for the device and find out it's power ratings. In your case 12V*.08A=0.96Watts. You will need something more substantial than a 2N4403. Rule one of electronics is don't buy from radioshack (this assumes that they actually have the parts you're looking for - not likely). When looking through a website or catalog they will normally clearly show the transistors polarity and it's power ratings. Choose appropriately. Note: This is not a Inventive/New Idea. This thread will probably be moved.
  3. You could set up a motion detector to toggle rec on your VCR or power or some other control method. If you have the ability to record on your computer there are programs out there that will let you setup an "Active" area and when it detects a certain amount of change from one video frame to the next it will start recording video to your hard drive. Try google for software.
  4. Are you looking to make or buy? I'm sure mouser.com, alliedelec.com, digikey.com, jameco.com someone has these to buy.
  5. This sight will make keypads anyway you want them with pictures, graphics, etc..... whatever. -----> http://www.spectrasymbol.com/ Send them an email with what you want or use their online quote system and they will give you a price. I have tried their products and they are great.
  6. Blueprint? You mean pinout or am I missing something?
  7. When I first started in electronics I first got desoldering braid then a desoldering bulb and then the spring loaded desolder pump like you had and then i finally bought the radioshack desoldering iron. I have had it for over 5 years now and it still works great. It really is one of the best things to come out of radioshack. It eats tips like crazy if you try to straighten pins while desoldering but sometimes its worth it (on a lot of boards they bend component leads before soldering and bending them while heating the solder is sometimes the only way to gets parts off undamaged). I say to any beginner who is messing with junked equipment for parts get a desoldering iron first and save yourself the hassle and headaches.
  8. If you included a price that would be better for you. I never hunt down a price. If a price is not lsted with the product then I move on and will find somewhere else to buy from that is willing to display their price for all to see.
  9. It's probably possible but if it's not possible through firmware/software it's not worth the time and effort in my opinion. Even tweaking the firmware/software of the phone would be a long and difficult unless you really knew what you were doing. I'm not saying I would be able to do it fast but if you have to ask then it wouldn't be a breeze for you. I hope you do find a way though.
  10. judging by your post and diagrams and everything else I would either buy a 12volt fan made for a car or buy a power inverter from walmart. Walmart has 140Watt (peak) power inverters for around $17-$20 which will be useful for more than just running a fan and probably cheaper than a home brew version.
  11. A few things to note. I have owned one of these and returned it days later. It does work but it is very touchy. You have to get the tip just right on the joint for it to heat up and most the time you do have to put some pressure on it. The problem is the instruction book specifically says do not press down on the tip or you'll break it. I sucks batteries way to fast. This device is only good to keep in a glove box for and emergency solder needs, that way the batteries have a chance to recover a bit from it's last use. The thing doesn't heat and cool as fast as it says. It heats up in a short time (20secs) but the longer it's on the longer it takes to cool. It normally takes awhile to heat up so by the time you soldered your joint the thing is to hot to touch for the next minute ..... not seconds. I have looked over the patent and the patent covers the idea and tip not the circuit that drives it, it might be under another patent. The thing does put off sparks when you first touch a solder joint. Melting an already existing solder joint is a lot easier then making a new one. When trying to make a new joint if you start the tool on the solder pad you will turn the pad red hot and melt it off the board, if you start it on the solder then when it starts to melt you lose the connection between the tips and it stops heating. If you get clumsy with the tip and it touches two pads at once you will send a bad amount of current through your circuit. My suggestion. Save your money.
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