Recent content by premelec

  1. premelec

    interface with 3x4 keypad

    Note you can read a key pad using single ADC pin and a few resistors [q.v. one wire keypad]
  2. premelec

    Calculate Square Root to two decimal places

    Not sure if it's of use - I used to use a routine on a Friden mechanical calculator [60 years ago] which involved subtracting 1-3-5-7-9 counting subtractions and shifting... Also taught my kids about squares with Y by Y marble arrays having them see how many marbles needed to be added to get...
  3. premelec

    Solar powered robot - Charging suggestions requested.

    FWIW there have been PV designs which use a cooling fluid [sometimes air] to use the thermal excess for heating water or house air etc and keep the panels cooler so they then have better efficiency.
  4. premelec

    Solar powered robot - Charging suggestions requested.

    Is weight a factor for your battery needs? lead acid is still cheaper and heavier... more tolerant of charge and discharge - however with all the lithium cell use good battery management systems are available - more information on how much power you need compared to how much is available would...
  5. premelec

    Switching positive volt

    PNP or PMOS transistors can be used to switch positive line.... mechanical relays still work ;-0
  6. premelec

    Automotive ignition pulse sensor

    Don't know if OP has resolved this... I have at times used an opto isolation structure made with neon tube [Ne2] shining at a distance on an LDR in dark sleeve or pipe insulated casing - with fiber optic or lucite light pipe if long.. The neon tube can take the HV stuff ok -Slow response ...
  7. premelec

    Thoughts on a Unique I2C-DAC Interface.

    Can you reduce Vref on the DAC? Or use a 10 or 12 bit DAC ;-0 - Possibly the fvr has too high source impedance for setting the DAC chip... you can use an LDR to reduce your 5v source... What is the driver's input impedance?
  8. premelec

    Pushbutton slew control with acceleration

    Welcome to this forum - an approach could be using a variable which is incremented or decremented depending on which button is pressed and that variable is involved in the timing... or if you need two different rates for which way you are going then use two variables... Decrement a timing...
  9. premelec

    Automotive ignition pulse sensor

    I think OP just wants to know if engine running or not... You can find the LM2907 in many OLD floppy drives for salvage... [If I recall correctly - been a while since I was into my piles of old drives... ;-0 ].
  10. premelec

    Automotive ignition pulse sensor

    Welcome to this forum... In past tests I found that putting a coil taped to the outside of an ignition coil gave a good signal; almost any pickup coil will do - old headphone or relay coil etc.... then put a 5 volt clamp on the signal - zener diodes etc to protect your microcircuitry - this...
  11. premelec

    AXE401 Out of stock. Is this a temporary situation ?

    @Buzby - an opportunity to get a neighbor kid into soldering addiction... ;-0 Ah the smell of flux smoke and hot epoxy etc... I'm with erco and built my first Heathkit about 1950 - I solder something pretty much daily though now it's often disassembly rather than assembly.
  12. premelec

    Non picaxe question - audio voltage divider

    Sometimes it's worth having small amplifiers at point of use and just distribute the audio on telephone wire... Lpads work and are energy inefficient.... We don't have any idea of what power level you are running... or the needed quality of the signal to be heard...
  13. premelec

    Best Solder and flux to use

    I like Ersin multicore .... 63/37 or 60/40 - haven't gone lead free... mostly smaller diameter - it's easier to not put on too much solder - fine solder and tip certainly help with SMD... I chase solder bridges with wooden toothpicks... [the smoking wood helps part the solder...].
  14. premelec

    Variable power laser

    Please give more information with regard to actual speeds / timing. Also note you likely will need a gate driver for a switched MOSFET if you use that to switch current [overcomes gate capacitance lag].
  15. premelec

    Free 9v Duracell coppertop batteries

    Hi Pongo - I'm not against the policy - just what happens to the partially used batteries by the thousands - I don't think they have any program to put the partially spent AAs to any good use... I am opposed to ear splitting alarms anywhere, anytime... ;-0
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