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  1. C

    digital clock

    Look. . .. he's not going to come back.
  2. C

    Trap Door Project: DC BATTERY BACKUP for 12VDC Linear Actuator

    Just use 8 D cells or two lantern batteries. These will last 5 years and a backed-up battery will only last 5 years as it will dry out. .
  3. C

    Clean square waves using a 555 timer?

    555 is a very nasty chip. It is not an "engineering chip" but just an electrical chip for a car project, where nothing matters. For low frequencies you will need to add a 10k and 1n between the 555 and the chip you are clocking with the 1n on the input of the chip you are clocking. Some chips...
  4. C

    self driven piezo

    We have already gone over this in another Forum. Are you NEVER satisfied?
  5. C

    Please help me with a simple circuit

    What is the V in a circle?
  6. C

    18650 stays @ 4.15 volts

    I realise that.
  7. C

    18650 stays @ 4.15 volts

    Connect the cell to 47R resistor and a 12v battery and include your meter. Read the charging current.
  8. C

    Why won't my TI CD4098B multivibrator give me a pulse

    Draw the circuit.
  9. C

    Power supply current problem

    Connect a 10R 10w resistor. Does it get hot?
  10. C

    diy metal detector

    Cannot be done.
  11. C

    Inductance value problems

    100mA is an enormous amount of current. I was thinking about 100uA to 1mA.
  12. C

    Inductance value problems

    How much output current do you want????
  13. C

    Adding a Diode or Two?

    IC1 does not like a voltage on its output pin that is higher than the input pin. When the power switch is turned off, the output voltage may be present for a short time longer than expected and the top diode conducts if this occurs, to prevent damage to IC1.
  14. C

    Can anyone help with finding this vintage capacitor?

    "I would be happy buying any number of these." I have 10,000 as lot number 4235A for $1,555
  15. C

    Novice designing circuits

    I design circuits for $1.00 per hour. $1.00 per hour is an enormous amount for me.
  16. C

    LM3915 with dc motor

    A BC547 is not good enough.
  17. C

    Difference between ground and -ve voltage

    THE POWER SUPPLY Sometimes you will see a circuit as shown in the first diagram with 12v or +12v on the top rail and 0v or a negative sign or the word "negative" on the bottom rail. In this case the word negative means earth or "chassis of a car" and we commonly refer to this as "negative...
  18. C

    serial regulator

    The figures should be: base current = 24 - 16 = 8v current = 8mA. All this means is this: the maximum emitter current can be as high as 50 x 8 = 400mA. but the actual emitter current is determined by the load. Doing the calculations in your head: The 1k resistor will take 15.4mA and...
  19. C

    serial regulator

    You are right. I read the circuit incorrectly. The only comment I can make is the fact that the transistor will deliver a maximum of about 300mA due to the gain of the transistor.
  20. C

    serial regulator

    What current flows through the zener when the switch is open?
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