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LostViking

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  1. I think this has been done with a string and a bell already. Of course you could use a rotating PIR, or maybe use IR emitters and detectors on the stakes to set a perimeter. Each stake has it's own power and noise source.
  2. OK, you measures some amount of potential. Now try to store that in a capacitor. If you can do that...
  3. The starting point of any journey is "where do you want to go?". You need to have an idea of what you want to do before you can figure how to get there. Each type of project and industry has different requirements. It doesn't always take high level engineering knowledge to invent something. To tell you to to go lean VLSI is to tell you to start down a path I want you to follow.
  4. Read it. There is nothing preventing you from transferring some of the charge from your recharged battery to the dead one. But you get nothing for nothing. First off no transformer is perfect so there will always be some loss, eddy currents, resistance in the windings... The bottom line is you can not transfer all the energy from one cell to the other by any method. The other thing to note is you know nothing about the state of charge for either battery. Current readings mean almost nothing. If you want to know what WAS in the battery you can measure the discharge over time and integrate. Me
  5. There was a small IC I saw years ago that would do exactly what you want. It's all in the chip. You do have to train it, but there is a secure and non-secure mode that uses the recognition threshold. It was something I was going to use to turn lights on and off as part of a home automation system. I did a web search and found something interesting from Phillips called the Hello IC. Give it a look see.
  6. I'd just run the batteries in series to get the higher voltage, then tap off at the 2.4V point for the lower voltage stuff. Simple.
  7. Shoot the q's and I'll answer what I can.
  8. It's hard to determine from the information. There may be two answers. First some alarms use magnetic sensors at windows and doors. This is simply a magnet and a reed switch that is pulled closed by the magnet when they are close. The second type might be actually an inductive sensor. It is usually excited by a weak oscillator and when metal is moved into the inductors field (it is part of the tuned circuit of the osc) the oscillator shifts in frequency and this is detected by other circuits. I hope this helps. If not please supply a bit more information. What sensor specifically?
  9. I could be wrong, but I think he is talking about the power LED on a device. Not power LED's as in high power. I also believe that the LED is being turned on now. He just wants to make this happen slowly rather than all at once. Could be wrong and it wouldn't be the first time. Hey eplanet, can you supply the missing details?
  10. I used to work for a company making current profilers. Sort of the same thing and they used piezo electric transducers. You will need to transmit a pulse at the target. Don't really need to know the doppler shift since you are not trying to measure the speed exactly, just determine if they are running or walking. What you do need to do is measure the time of flight. This is the difference between when you transmit and receive. You do not transmit continuously, but rather in pulses when you want to detect a target. Since this MUST be a uP design you would then compare the time against limits
  11. Are you talking about the wind up clocks? Has a dial and arms for hours, minutes, seconds...? How skilled at small stuff are you? :) You can use the minute hand as a contact. Then drill a hole in the dial face and add another at the 12 position. This should be a wiper that can be pushed out of the minute hands way as it passes. Now build a timer and buzzer circuit that runs for N seconds and resets. Use the above wiper/contacts as the trigger input. Of course for a lot less trouble you could buy a digital clock, but what fun is that?
  12. Omni, You are very correct. There is no simple circuit for something like this. The cheapest approach is to use something already made and modify it to work. Properly constructed the environment isn't really a big problem. Most of this stuff would not be very sensitive and even with a uP design temp is not a big problem. However, as Omni said it may be a MUCH better idea to use something that is already proven. 1984 Corvettes used an all LCD dash. Not LED's like you asked for, but it is an all digital dash. I'm sure there are others and I know for a fact that the aftermarket makes LCD dashes
  13. Take a look at the Maxim MAX878. It can do what you need. The circuit in the datasheet may be all you need. This part will regulate the voltage down, but if the input drops below the needed voltage it will switch over to BOOST mode automatically. Works down to 1V input too so you can really get all the batteries have.
  14. Apologies to the board. I usually just attempt to answer the q's and not judge why people are asking them or call them names. I guess calling all Americans criminals or saying that all the criminals and guns in Canada are from America, a couple day's before Veterans Day (you civilians can call it Memorial Day, but we still call it Vets Day!) set me off a bit. Humbly crawling back into my corner.
  15. Never had a problem with mine. Used both passive and active pickups. No problems. Try it.
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