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  1. CDRIVE

    Old multimeter

    This may seem like a lame question but are you zeroing the meter first? Chris
  2. CDRIVE

    Transformers

    Since this was your original question the answer is no. Here's what the outputs of a 1/2 wave rectifier vs. a Full Wave Bridge look like prior to filtering it with a capacitor. The transformers in both circuits are 4:1 Step-Up Transformers. Thus they output a voltage 4 times the input voltage...
  3. CDRIVE

    Transformers

    Looking at all three circuits posted I find an irony embedded in them. The first one is the oldest design, which uses germanium PNP's. Yet that old design will probably fit a basic communications precept better than the other two. I'm referring to an AM transmitter will (ideally) not pull the...
  4. CDRIVE

    GPS NMEA, Failover Circuit upgrade attempt.

    If 330Ω doesn't provide enough LED brilliance for your liking a 220Ω limiting resistor will. It provides both max permissible current (~20mA) for both the LEDs and the Picaxe I/O pin. Chris
  5. CDRIVE

    GPS NMEA, Failover Circuit upgrade attempt.

    Here's an "R vs I" plot for a typical low current Red LED. V+ = 5.0V Chris
  6. CDRIVE

    GPS NMEA, Failover Circuit upgrade attempt.

    No... recalculate for Red LEDs. To insure that the Picaxe I/O pin currents are less than.. "I=" <= 20mA R should = ~ 330Ω. EDIT: It's never a good idea to run a component near its maximum parameter. The Picaxe manuals specify 330Ω resistors because they'll run the LED at about 10mA, which is...
  7. CDRIVE

    GPS NMEA, Failover Circuit upgrade attempt.

    In my last post I was referring to the LED's directly driven by the Picaxe. You may want to recalculate the limiting resistor for the two LEDs powered by the 12V source too. Running LEDs at their max rated current will shorten their life span. On another note 1N914's are switching Diodes...
  8. CDRIVE

    GPS NMEA, Failover Circuit upgrade attempt.

    Constantine, if your LED's are Red your current limiting resistors should be 330Ω. Chris
  9. CDRIVE

    GPS NMEA, Failover Circuit upgrade attempt.

    Why did you remove the protection diode across the relay coil? Just a tip when posting schematics: It's good practice to label components, IE... Rn, Cn, Qn, etc. This way we can more easily reference them in our replies. Ash, I see you've put considerable time into this topic. My apologies...
  10. CDRIVE

    GPS NMEA, Failover Circuit upgrade attempt.

    Your LED's Anode-Cathode is reversed and it's also missing a limiting resistor. Also, you can't feed a 5V regulator with 5V input. Chris
  11. CDRIVE

    Measurement -2.5 +2.5 with ADC

    azadfalah, I made note that you clicked "Liked" in regard to the schematic and transient analysis that Bob took the time to draw. That's all well and good but where's the "Thank You"? Is it possible that you turned in this class assignment and have moved on to the next one? If my suspicions...
  12. CDRIVE

    Trying to make a simple LED blinker but it doesn't work...

    Yes, you can wire 1.5V cells in series with a 9V battery. ;) Chris
  13. CDRIVE

    Trying to buy the right sockets for my PICs

    Presumably, those must have been authored by people that either solder like a welder joining 1/2" thick I Beams or have little faith in the abilities of others to not fry what what they're soldering. Chris
  14. CDRIVE

    Home Project wiring help

    You posted an Ebay link to the motor changeover relay and a video but I didn't see a link to the RF transmitter and receiver module you purchased. Did I miss it? Chris
  15. CDRIVE

    Troubleshooting a diode voltage drop

    Actually that's a very good question. Doing so would have required a Diode with a higher 'continuous' current rating. Other than that... I don't know. I can tell you that it was standard OEM design and used on all models and manufacturers. Chris
  16. CDRIVE

    Troubleshooting a diode voltage drop

    It may be worth noting that protection diodes aren't or weren't always wired in series with the supply input. Things may have changed since I had a land mobile / marine electronics shop but back then the protection diodes were wired like this... The concept was that a reverse polarity would...
  17. CDRIVE

    Troubleshooting a diode voltage drop

    Hey, I forgot to mention that the Diode saved your a$$. If it weren't for that 'Reverse Polarity Protection Diode' you'd have fried the board! Chris
  18. CDRIVE

    Troubleshooting a diode voltage drop

    You'll be pleased to know that when I'm proclaimed King of the world my first decree will be that ALL coax power plugs shall have a ( + ) center pin. Failure to comply with this standard will require forfeiture of a testicle! :D Chris
  19. CDRIVE

    How to control the speed of a 24vdc pump from circulating water temperature?

    Hop, I could be wrong but I think USCG regulations will accept only Propane for cooking and heating. Though, possibly electric cooking & heating will pass muster. On that note it's my personal opinion that land lubbers should first own quite a few holes in the water before considering living...
  20. CDRIVE

    How to control the speed of a 24vdc pump from circulating water temperature?

    Stu is a seaman not an EE or ET. It's doubtful that he's even an electronics enthusiast. IMHO your questions should reflect this. Stu, if you find that change in water temp vs the change in motor speed (< >) is too fast for your liking a large Cap in parallel with the .1uF Cap will slow any...
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