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  1. #51
    Cheers George.... i had my fingers crossed... but no joy. the motor body is 30mm i could do with at least 15mm to play with for a housing and bearings,,, those you linked are 38mm and a good bit of that length is taken with the knife,, nice try though xx

    irving... the servo testers are between a fiver n tenner ebay... the rest of what you ask is errr... rocket science..
    i have read somwhere that the puls rate is way to high for mach3 and would need some kind of conversion

    im sure a man like you could rustle one up in your dinner break :)
    Last edited by blackburn mark; 12-08-2010 at 12:25 PM.

  2. #52
    ecat's Avatar
    Location unknown. Last Activity: 08-02-2014 Has been a member for 6-7 years. Has a total post count of 157. Received thanks 5 times, giving thanks to others 8 times.
    I'm guessing we are talking about standard RC parts here so, the servo tester most likely outputs a signal of 20ms period. The width of the pulse within this 20ms period determines the output of the ESC. Actual values and their relation to each other depend on the hardware used.

    Can the ESC be driven from a 0 to 10v signal? Not directly. I'm sure there'll be something on the web to suit or maybe this is another job for a friendly PIC.

  3. #53
    if you guys dream up a simple way of of conecting to mack3 ill have some of that :naughty:

    im thinking of basterdising a lazor rev counter... can anyone tell me... will i get away with removing the lazor diode and pickup and extending them out onto my z axis and put the lcd somwhere more sociable?

  4. Quote Originally Posted by blackburn mark View Post
    im sure a man like you could rustle one up in your dinner break :)
    Quote Originally Posted by ecat View Post
    I'm guessing we are talking about standard RC parts here so, the servo tester most likely outputs a signal of 20ms period. The width of the pulse within this 20ms period determines the output of the ESC. Actual values and their relation to each other depend on the hardware used.

    Can the ESC be driven from a 0 to 10v signal? Not directly. I'm sure there'll be something on the web to suit or maybe this is another job for a friendly PIC.
    This is an easy job for a single 14pin PIC, two small potentiometers (to set min and max speeds), a diode, a couple of resistors and two capacitors. The diode/resistor/capacitor combo forms a charge pump that converts the fast PWM signal from MACH3 into a voltage which is sampled by the analog-digital converter in the PIC. The same A/D converter samples the settings of the two pots to determine high and low speed limits. The PIC then generates a PWM output that varies according to the incoming voltage from MACH3. A speed sampler could be included in the same device and closed loop functions could be added to maintain set speed against load... With a bigger 20pin PIC the rev counter display could be added... price of the PIC, about £1, total cost <£15 if built on stripboard or enough were built to make setting out a PCB viable. Basic software would take a few days... bit longer for the closed loop stuff...

  5. #55
    Hi Irving,

    1. This explains far better than I could:
    http://www.servocity.com/html/how_do_servos_work_.html

    2. Servo tester is £5 - £15
    http://www.fast-lad.co.uk/store/prod...oducts_id=1716
    The potentiometer on the tester controls the width of the pulses, and replaces the signal it would otherwise get from the reciever. This signal moves the output arm of the servo motor to the required position, or for the throttle, the engine to the required speed. It is fully proportional.

    I wondered, with my limited electronics knowledge, whether the pot could be removed (which must just provide the pulse generating part of the servo tester with a 0 - 4.8v output) and via a magic box the Mach3 0-10v could be connected instead.
    I'm sure you could come up with something along these lines or better !

    Does this help you with a better plan?

    Ah, you've already replied. Looks like you have it in hand!
    Building a CNC machine to make a better one since 2010 . . .
    MK1 (1st photo), MK2, MK3, MK4

  6. Quote Originally Posted by blackburn mark View Post
    if you guys dream up a simple way of of conecting to mack3 ill have some of that :naughty:

    im thinking of basterdising a lazor rev counter... can anyone tell me... will i get away with removing the lazor diode and pickup and extending them out onto my z axis and put the lcd somwhere more sociable?
    dont bother... the prpoblem with the laser diode ones is that they are sampling devices... press to read... as the laser diode cant handle continuous operation. Its a lot simple to do a slotted vane type approach and one of the many solutions discussed in Rick's Boxford 260VMC thread

  7. Quote Originally Posted by routercnc View Post
    Hi Irving,

    1. This explains far better than I could:
    http://www.servocity.com/html/how_do_servos_work_.html

    2. Servo tester is £5 - £15
    http://www.fast-lad.co.uk/store/prod...oducts_id=1716
    The potentiometer on the tester controls the width of the pulses, and replaces the signal it would otherwise get from the reciever. This signal moves the output arm of the servo motor to the required position, or for the throttle, the engine to the required speed. It is fully proportional.

    I wondered, with my limited electronics knowledge, whether the pot could be removed (which must just provide the pulse generating part of the servo tester with a 0 - 4.8v output) and via a magic box the Mach3 0-10v could be connected instead.
    I'm sure you could come up with something along these lines or better !

    Does this help you with a better plan?

    Ah, you've already replied. Looks like you have it in hand!

    Thanks... I know how RC systems work, just wasnt sure on the PWM characteristics, its 30+ years since I built and flew anything (but my 10y old nephew is showing an interest so maybe I'll resurrect that... along with the 47000 other projects)

    MACH3 doesnt produce a voltage just its own fast PWM train, which has to be converted to a voltage. My solution does that, tho it would be possible to use the PWM/ECCP (count and compare) function in the PIC to measure it directly, but that needs a PIC with two PWM channels and the 14pin ones only have one. Needs more software to be written too!

  8. #58
    cheers irving, ill have a butchers

  9. #59
    I'll post more on Tuesday (I'm on holiday at the moment so no internet!) but I'm pretty sure mach3 will do the PWM. As ecat said the period for the ESC is 20ms, so 1/0.02=50hz. This next bit may be wrong, but anyway...running mach3 on 25khz kernel speed with 50hz PWM gives 25000/50=500. So that means you get 500 'steps' between 0% and 100% duty cycle. The ESC is probably 255 steps anyway, and if it's 1023 then it's not really an issue.

    You'll probably want to put an optocoupler between the parallel port pin and the ESC just to be safe if the ESC doesn't already have one. Oh also if mach3 is 0 to 10v then just use a voltage divider to reduce that to 0 to 5v. Two 10k resistors should do the trick, or anything really it's not critical.

    If that doesn't work then I'd go for the PIC option. I've had a PIC controlling servos before from a potentiometer...it shouldn't be difficult.

    Jonathan
    PS Have a look on eBay for servo testers. I think you'll find them cheaper.

  10. #60
    yo jonathan.... sounds interesting, a bit complex for a simple soul like me id need walking through the whole procedure

    have you had any joy with the brake ? i found a vid on youtube where someone had used a mechanical calliper on a disk
    Actuated pneumatically,,, id prefer to use a motor and screw with a spring as a buffer

    if you have any old slit saws you could use one of these as the disk
    i havnt desided whether ill take the simple road and use a rotary table or build a fast mover with a disk brake

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