MERG Kit 681 - Point Motor Servo Mount

Discussion in 'Other Electronic Interfaces' started by paul_l, Feb 18, 2016.

  1. paul_l

    paul_l Staff Member Administrator

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    The MERG Point Motor Mount kit (Kit 681) contains enough parts to make up 6 mounts. They are designed to use the 9g size model aircraft servos. In addition Kit 682 provides parts to convert them from vertile action to horizontal action, and Kit 683 contains 12 micro switches and screws nuts etc to mount on the brackets.

    Price Kit 681 £6.36 for 6 (£1.06 each), Kit 682 £1.86 for 6 (31p each), Kit 683 £7.20 for 12 (60p per micro switch)

    9g servos - I got mine from Amazon for £15 for 10.

    I am using mine in verticle mode, with 2 micro switches, so total cost per point motor is approx £3.76.

    [​IMG]

    The brackets are 3D prints comprising 3 main parts
    [​IMG]
    The pivot piece (middle) fits through the top square hole - "some filing may be required", yep i'd agree with that.
    Once fettled into shape, the servo is inserted - the mounting screws supplied with the servo are used to secure it to the bracket. I found I had to trim the top servo mount to keep the pivot bar level.
    [​IMG]
    Next the pivot arm and wire.
    I had to shorten the servo arm to allow the pivot arm to fit over it.
    The piece of piano wire is bent through 90 degrees 4mm from the end, then treaded through the top of the arm.

    [​IMG]
    Jobs a good un.

    The bracket can hold up to 4 micro switches - still to fit mine.

    Paul
     
  2. Toto

    Toto I'm best ignored Staff Member Founder Administrator

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    You'll have to get these operational and give us some feedback ........... along with a video of course.
    cheers
    toto
     
    scottystitch likes this.
  3. jakesdad13

    jakesdad13 Staff Member Moderator

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    I like the look of these, I assume you will control them with DCC, are they suitable for DC as well? and presumably they are MERG members only to purchace?

    Cheers, Pete.
     
  4. paul_l

    paul_l Staff Member Administrator

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    Hi Pete

    There are several ways to operate the servos,

    MERG do the Servo4 kit - http://p1mrc.com/p1mrc/view_topic.php?id=162&forum_id=12 £6.30 to operate 4 servos, these units are controlled by an input, could be from a switch, or output from a relay, DCC accy decoder, arduino etc etc. Needs setting up via a PC serial port or the ServoSet2 dedicated standalone setup device (only 1 required) £20.00

    Also available from MERG is PMP18 EzyPoints v3 £1.86 controls pots on the board to set, start point, end point and speed.

    Heathcote-electronics also sell a servo controller unit
    Megapoints also produce a 12 servo controller unit.

    If you are willing to get your hands dirty, then the arduino and raspberry pi route opens up a vast array of options.

    A standard arduino Uno or Nano (or compatable / clone) can control approx 8 servos via the analog output pins, however, this can be increase by adding I2C servo expansion boards

    http://www.modmypi.com/raspberry-pi/breakout-boards/adafruit/adafruit-pwmservo-driver-16-channel-12-bit-pca9685/?search=servo

    You can also add multiple boards controlled from the 1 arduino, the arduino digital input pins can have switches attached to it for control.
    I would point out that as the servos are controlled via dc voltage signals, I would want to keep the wire lengths fairly short, and the cost of a Nano clone is cheaper than the adafruit servo driver board. The last lot I bought from China cost £17 for 10. I also knocked up a circuit to feed DCC signals into the arduino which then lets you use the arduino as a DCC accy decoder.

    Paul
     
  5. jakesdad13

    jakesdad13 Staff Member Moderator

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    Thanks Paul, way too complicated for me I,m afraid, think I will stick with wire and tube or peco motors and stud and probe :whatever:.

    Cheers, Pete.
     
  6. paul_l

    paul_l Staff Member Administrator

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    Hi Pete

    A couple of years ago I would have said the same, the MERG kits are a great way of learning, as they give simple but comprehensive build instructions, but also if your interested, a description on how the circuit works, and also fault finding / troubleshooting tips.

    If you can solder wire to rail, you can build one of these kits.

    Paul
     
  7. ianvolvo46

    ianvolvo46 Staff Member Moderator

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    Ok ... I can look to start with a basic kit eventually ... but I'm keeping mi knitting needles close at hand! Ian vt:scratchchin:
     
  8. Keith M

    Keith M Staff Member Moderator

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    I've used a couple of the 'Servo 4' kits to control my level crossing gates, using the servo mounts with the same 'Tower Pro' servo's. The kits are well thought out and quite easy to build, and as Paul says, if you can solder a wire to a rail, you can build these kits. I've not got around to playing with the Arduino I bought some months ago yet since I'm more 'hands-on' with the practicals rather than 'headbanging' theory and learning to program, but I'll get there eventually. If you're a MERG member, you can download the servo setup software to a laptop and go from there, so no need to buy and build the ServoSet unit.....even I managed to do that and set up my crossing gate servo's, so if I (as a 'P.C. Duffer") can manage it, anyone can!:avatar:

    Keith.
     
  9. scottystitch

    scottystitch N Gauge Society Publicity Officer Full Member

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    Paul, I've just come across this thread as I was about to ask the question "can someone show me the kit of parts, etc. for the MERG servo mount" and lo, and yes, behold you predicted my question two years ago.

    I am going to be using MegaPoints for control of my 60-odd points on Glasgow North, so looking for a cost effective mount for the servos. Next, thoughts will turn to Frog polarity switching. The thought of wiring up 120 microswitches doesn't fill me with much joy. And then another 120 for LED point route indication.......... I'm tempted by MegaPoints' Frog Relay units, but they need the control board as well and that would add to the cost. That said, it would be a very simple plug and play method. And it's still cheaper than going down the Cobalt route (of which I have a couple of dozen, but I think I'll use them on smaller projects, like Tormouth)
     
  10. paul_l

    paul_l Staff Member Administrator

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    Have a look at the Merg Servo 4 unit, or if you really feel like going down the Dark side route make arduino controllers.
    Viccy Road uses two Servo 4 units with an arduino as the DCC accy controller sending the signals to the servo4 units.

    I wouldn't worry about the wiring of the limit switches, its only 3 wires and the servo mount will let you attach upto 4 micro switches, giving you options for feedback and interlocking. Of course to be correct you should use two limit switches one for each end of the throw of the point blades - and that's only two micro switches and 4 wires :avatar:

    Paul
     
  11. scottystitch

    scottystitch N Gauge Society Publicity Officer Full Member

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    Thanks Paul.

    Control of the points/servos will be via switches on a mimic panel. I just want a nice simple set up - throw a switch, wiggly amps do their thing, the servo moves.

    Re the micro switches - one at the end of travel of both throws of the servo = 2, then the same again to switch the relevant LED on to indicate the route set on the mimic panel, no?
     

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