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  1. gorgon

    Trying to understand AA batteries and their capacity

    Even if the theory say this is possible, it is not practical in real life. To manage this your batteries needs to be exact equal in voltage. If not the battery with the lowest voltage will 'short' the one with the higher voltage and draw power from that until the capacity/voltage is down to the...
  2. gorgon

    what is negative voltage/power supply ?

    In my world the reference point is called 0V, and has little to do with earth or ground. Sometimes this reference point is connected to ground or earth. Being a 0V point, it also indicates that there is both voltages more positive and 'more' negative. This is then the +V and -V we're talking...
  3. gorgon

    I want to make a battery pack that can make 7.5V at 3.0A.

    If you use a 12V 7Ah SLA and a smal DC-DC switch mode converter generating 7.5V with a capacity of at least 3A. With a good efficiency rate, like >90-95% you should be good for 7-9+ hours max load. To charge it you can use a cheap car battery charger. This will not be pocket sized, but...
  4. gorgon

    Problems substituting a relay

    If the original relay had a 1200ohm coil, it would be a 20mA relay, corresponding with the current in the LED(minus the 220ohm). This means that you can't get 40mA out of the circuit, without some changes in the drop capacitor from mains. I would be very sure that you do the right calculation...
  5. gorgon

    What switch do I need?

    What is the voltage and the current rating for the circuits you want to switch? You need to supply a little more info. TOK ;)
  6. gorgon

    I want to make a battery pack that can make 7.5V at 3.0A.

    As far as I can see you have not said anything about how many hours you want to run your system on the battery pack? Another point is how portable you want it to be? TOK ;)
  7. gorgon

    4049 hex inverting ic

    The main problem with Schmitt trigger based oscillators, is that you can't be sure that the threshold levels are equal enough between batches from the same manufacturer and, certainly not between different manufacturer. This problem is of course only present if you plan to produce something over...
  8. gorgon

    Correct way of converting 12v down to 3.3 for a pin input?

    It could be that the IO on the Pi is 'TTL' compatible, and that will have an impact on the electrical logic levels. This should be defined in the electrical specification of the Pi's IO. That said, it is always good to get as crisp levels as possible, due to the signal vs. noise quality...
  9. gorgon

    Correct way of converting 12v down to 3.3 for a pin input?

    The voltage you refer to is the isolation voltage, or the potential voltag difference between input circuit and the output circuit. It has little to do with the voltages you use to drive the signal through. What type you select is mainly depending on the frequency of the signal you want to...
  10. gorgon

    Correct way of converting 12v down to 3.3 for a pin input?

    If you are using this to read DC signals from a motor, I would highly recommend an optocoupler between the motor and the Pi. One for each signal! TOK :)
  11. gorgon

    NPN Transistor

    Put a 10k resistor in series with the base. You are burning off the base emitter diode. TOK ;)
  12. gorgon

    3.3V

    Most modern microprocessors and microcontrollers use 3V3 as IO voltage these days. Most of the 3V3 IO is 5V tolerant for the inputs, but you need to take a bit of care when driving 5V logic with 3V3 outputs. I use to specify 5V HCT logic for that since the TTL levels is compatible with the 3V3...
  13. gorgon

    Help: need to find PCB design + assembly companies

    I checked other forums, and found different users with almost the same text and same link address placed there. TOK ;)
  14. gorgon

    Help: need to find PCB design + assembly companies

    Sniff, sniff do I smell spam? TOK ;)
  15. gorgon

    Generating a 5V Clock Signal

    Not if you see the oscillator from the top. The question is, does it work? If not, have you connected it different before? Have you shorted the output to 5V or 0V? How do you know it doesn't work? I know it's of little help but I've used a number of canned oscillators in the past, and...
  16. gorgon

    How to connect POT and how this regiulator based charger behaves?

    If you use 13.6V you should be relative safe. You may use this as a continous standby charge voltage. But this is at an ambient temperature of around 25 C. To compensate for changed temperature, you should compensate the voltage with −0.0235V/°C. The datasheet on the battery you have, will...
  17. gorgon

    How to connect POT and how this regiulator based charger behaves?

    TOK is my signature TOK ;)
  18. gorgon

    Need help identifying a connector

    JST is a manufacturer, but the pitch need to be more specific. There are 1.8, 2.0, 2.2, and 2.3 mm variants. Take a look here http://www.jst.com/ TOK ;)
  19. gorgon

    Repairing a toaster..

    Well, if you measured the resistance with the mains connected, I would assume that your meter is toasted. Pun intended :) First of all, never ever do resistance measurements on a live mains wire. If you have done that before, no wonder the meter is acting up. To control the meter, put it...
  20. gorgon

    How to connect POT and how this regiulator based charger behaves?

    For a lead acid 12V battery you should never set the fixed voltage higher than 13.6-8V, depending on the ambient temperature. For a higher temperature you need to reduce the voltage some. If you try to charge over time with a higher voltage, the battery will heat up and eventually dry out or...
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