Relay help needed please ;)

Discussion in 'General Electronics Chat' started by Leckyuk, Jan 1, 2011.

  1. Leckyuk

    Thread Starter New Member

    Jan 1, 2011
    My current project is a digital jukebox. I have built a cabinet and suspended an old flat screen monitor and converted it with a touchscreen kit. The jukebox software allows a keyboard interface module to be purchased which has screw terminals in which you can attach various items that will emulate the pressing of a key on a keyboard. I decided against purchasing one of these as I had an old keyboard lying around so decided to modify the control board instead.

    One of the software options is that a coin acceptor can be added. The acceptor ultimately needs to complete the circuit that corresponds to pressing the number 1 button on the keyboard. I have wired the keyboard and attached a microswitch which is all working correctly.

    I purchased a coin acceptor but unfortunately the specification sheet is very vague! I have a relatively electronic mind but have never really worked on a tiny scale.*

    I decided the best way to wire the circuit was to remove the microswitch and replace it with a relay. The coin acceptor is quite a nice unit as it can accept 3 different types of coins and when you put the coins in it sends the required number of pulses via a 5 volt signal. I purchased a 5v mini relay from maplin and wired it all up correctly but it just wouldn't work. I've realised now that the 5v pulses are at very very low ampage. The relay I bought I think is just simply to big for the circuit. I've tested it with 12v feed and the relay functions perfectly.*

    The spec of the coin acceptor is a working current of 65ma which I assume is the output pulse. I have tested the unit and it is showing 5v on my multimeter but the only way I could really check the pulses and that they were functioning was by attaching a tiny led which was lit but very very dim. The pulses are quite fast so I need a relay or anything you might be able to suggest that will have a quick response time and be able to function at such low amps.

    Thankfully the keyboard side of the relay carries little or no current and simply requires that circuit to be closed in response to the pulses.

    Sorry to have gone on so long but do you have any ideas for what I can do to rectify this situation please? *I have searched the Internet for very small relays but just have no idea which one to buy!

    Any ideas/solutions you could offer me would be greatly appreciated.
  2. Leckyuk

    Thread Starter New Member

    Jan 1, 2011
    Hi all, left this in project threads too but thought it might have been wrong area. Pardon my ignorance but what would be the best option to get my coin acceptor which gives off 5 volt pulses but at such low ampage it will barely light a tiny led, to operate a key function on a pc keyboard. I've re wired the keyboard so the required key is now two wires. I tried a 5volt relay but the pulses are just too weak to charge the solenoid. Anyone got any ideas what the best option will be?
  3. hgmjr

    Retired Moderator

    Jan 28, 2005
    Two threads about the same subject is bound to cause confusion. I have merged the two threads into one.

    Leckyuk likes this.
  4. Leckyuk

    Thread Starter New Member

    Jan 1, 2011
    Apologies to those of you more electronically minded than myself but I can see how my post must have been way beneath you all!!!! For those who aren't so electronically minded and might be interested what I did was add an additional circuit which was running 5 volts directly from the psu of the pc. I attached a transistor (which I admit until today had no idea how the worked) which I ripped from an old iPod dock which wasn't working. I then simply used the pulses from the coin acceptor to activate the transistor which in turn sent the required 5volts with enough ampage to the relay and hey presto, it worked!! Took a bit of fiddling to work out the correct connections on the transistor but got there in the end!
  5. marshallf3

    Well-Known Member

    Jul 26, 2010
    Congrats, that took some thinking. I saw your original thread but I figured someone would jump right on it since it was such a simple problem and you were very descriptive in what you were asking.

    Guess a lot of us let you down, sorry about that.