Pulse Multiplier/Divider - Need Some Help Please

Discussion in 'The Projects Forum' started by loewem, Jan 26, 2016.

  1. loewem

    Thread Starter New Member

    Jan 25, 2016

    I own a car wash and have been slowly learning the electronics/electricity aspects of repair and maintenance. I've been able to muddle my way through just about everything I've run into so far, but I've run into a brick wall with an improvement that I've been trying to complete. I'm hoping to find out if what I'm thinking about is possible.

    I have an Auto Cashier that accepts payment for automatic car washes. The cashier has four price/wash options that are selected by pushing the appropriate button. My understanding of the way the cashier works is that for the first wash pressing the corresponding button generates 5 electronic pulses which tells the unit how much $$ to collect and which wash to provide. The second wash/button generates 6 pulses, third button 7 pulses and fourth button 8 pulses. The button and resulting pulses correspond to the cost and wash package.

    I purchased a credit card reader that I successfully installed two other places in my wash. One I installed on a self-serve meter box and the other I installed on a token machine. The credit card reader comes with an "isolation interface adapter" which allowed me to tap into the coin mechanism on the meter box and the $5 bill wire on the token machine bill validator. So, the pulses generated by the coin mechanism or the bill validator tell the card reader how much $$ to charge the credit card.

    Since the auto cashier operates on 5, 6, 7 or 8 pulses I would only be able to charge $5, $6, $7 or $8 for the corresponding washes (or increments of those amounts ($10, $12, $14, $16, etc.).

    My question: Is there a way to convert the pulses that the auto cashier generates to a different number of pulses to the credit card reader? For example, 5 pulses on the auto cashier would equal 6 pulses to the credit card reader, 6 pulses to the auto cashier would equal 8 pulses to the credit card reader, etc. I would need something that could be easily changed as prices change. I think it is possible, but I'm not sure where to start.

    Any thoughts would be greatly appreciated.
  2. AnalogKid

    Distinguished Member

    Aug 1, 2013
    Several people will suggest a microcontroller-based design, and your application is ripe for one. But that requires writing a program to do the pulsing, plus some kind of user interface for reprogramming the conversion factors. The alternative is a medium-complexity logic circuit, with something that counts the incoming pulses and decides when the counting window should close, followed by a digital converter that turns the incoming pulse count into the numbr of output pulses. this goes to a presettable down counter that then counts out output pulses until it reaches zero. Experienced amateur level and above.

  3. absf

    Senior Member

    Dec 29, 2010
    Yes, a micro controller like PIC or AVR can do that. But why does a credit card reader need pulses?

  4. Colin55


    Aug 27, 2015
    You really need a micro because you want 5 different inputs to emerge with 5 outputs. And next time you want the 5 outputs to be completely different values.
  5. loewem

    Thread Starter New Member

    Jan 25, 2016
    Thanks for your replies/help. The credit card reader is made by a company named USA Technologies. Their primary business is the vending machine industry. The car reader comes wired for plug and play using Multi Drop Bus technology, but they also provide an "isolation interface adapter" for situations like mine where electronic pulse is used rather than MDB. So, I think the card reader relies on pulse because the auto cashier uses pulse.
    absf likes this.
  6. crutschow


    Mar 14, 2008
    Since you want to add differing pulse amounts to the various pulse sequences, I also think a microprocessor is likely the easiest way to do this interface.
    As far as reprogramming the device for different conversion factors, one way is to program the micro to accept values from dip switches, or rotary 10-position BCD or 16-position binary-coded hexadecimal switches on the board.
    You could have one switch for each of the pulse sequences, 5, 6, 7 and 8 (4 switches total). The position of each switch would tell how many pulses to add to a particular sequence.
    For example, if the 6 pulse sequence switch was set to 2, the micro would detect the 6 pulse sequence and then add two pulses at its output.

    If you're not familiar with programming I recommend a micro that can be programmed in the Basic Language such as those from Parallax or Picaxe for the relatively simple programming requirement you have.
    Others may recommend some C language variant device such as the Arduino but I find C very cryptic and more difficult to learn as a beginner.
    Last edited: Jan 26, 2016
  7. hp1729

    Well-Known Member

    Nov 23, 2015
    What type of bill acceptor do you have? Typically the number of pulses for bill denomination are set by switches on the bill acceptor.