I'm sure newbee's are troublesome but???

Discussion in 'General Electronics Chat' started by tbeaver, Oct 4, 2009.

  1. tbeaver

    Thread Starter New Member

    Oct 4, 2009
    6
    0
    I've taken on a project of changing over a friends mobility vehicle, A 24 Vdc powered three wheeled rig. We purchased a " KBBC SERIES
    MICROPROCESSOR CONTROLLED
    BATTERY POWERED DC/DC
    Variable Speed Motor Control

    http://www.kbelectronics.com/data_sheets/d905.pdf

    My questions are, P1- the 1 and 2 wires to the electromagnetic brake, Are they ref to another component or is it a relay that when the drive is commanded to stop, an output relay closes to short motor leads together. This action will act like a dymamic brake and impede motor travel. As shown on page 2 ( CYCLE J7) at this link?

    http://www.kbelectronics.com/manuals/kbbc_m_manual.pdf

    And what type of limit switch should be used for the " stop limit on P-3 of above link.???

    And my last question just to make sure, on the direction switch, would that be a SPDT centre Off ???

    Its not easy to get questions answered these days. Radio shack is a joke. So i want to thank you in advance and hope i put in enough info to make it easy.
    tbeaver
     
    Last edited: Oct 4, 2009
  2. tibbles

    Active Member

    Jun 27, 2008
    249
    3
    a bit specialized this one. anything other than a straight swap could be tricky.are the existing motors/electromatic brake compatable with the contr0ller,for instance,
    i was once asked to repair one of these, i was expecting a couple of relays and a distribution box. till i took the lid off.....
    i hope you manage
    have you tried talking to your local chair retailer they usually have a repair deprtment who probably works with these every day.
    regards
    dougal
     
  3. tibbles

    Active Member

    Jun 27, 2008
    249
    3
    ps
    i think the electromagnetic brake as you suggest may not work.i know it can be used to decellerate but isnt it more likely to be a conventional friction brake but actuated by solenoid or something.
     
  4. tbeaver

    Thread Starter New Member

    Oct 4, 2009
    6
    0
    This is an older style buggy. It only has one 12/24 Vdc motor and transaxle 1-2-3-4-5- forward plus reverse. So really all i'm attempting is a smooth motor acceleration. If you looked at the links, this control board has alot of features.

    What I really need to know is on the P-3 directional setting for maintained switching. Is the run forward / stop / run reverse just a ON-OFF-ON SPDT with a centre off?

    And what to use for the limit switches?

    Any help would be wonderful. Before this I thought electricity ran down hill, or is that plumbing?? lol

    Anyway please take a minute and look at the links. There is no more old wiring in the buggy. I'm starting from scratch.

    tbeaver
     
  5. Skeebopstop

    Active Member

    Jan 9, 2009
    358
    3
    I haven't really read this thread but from glimpsing here are some insights:

    - Electromechanical brakes are built into motors. They are 'normally' on (spring loaded) and you energize them to open. Typically 24V @ 500mA or more.

    - Limit switches, just use something that fits your package and voltage rating. If it is a big car proximity switches are nice and reliable.

    - The run/stop/rev switch requires a SPTT (single pole, triple throw) type relay or switch (turn dial type switch perhaps?). Depends if you need to make this automatic. A SPDT (single pole, double throw) with a 'not energized disconnected' configuration would also work. The Run forward and Run Reverse pins will have pull ups or downs on them so that when in the 'stop' position they both pull down or up and the micro knows this, as when it switches to run or reverse one of the pins drives high (or low depending on spec).
     
  6. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    Regenerative breaking is basically a dead short on a motor, using the generator aspect of the motor to create significant drag.

    I'd never heard about electromechanic breaks. Learn something new every day I guess.
     
  7. tbeaver

    Thread Starter New Member

    Oct 4, 2009
    6
    0
    I want to thank you guys that did reply, this stuff is new to me and i think i got over my head a little. although I can't help much this will be electronic forum that i tell everyone about. Great info here.

    tbeaver
     
  8. Skeebopstop

    Active Member

    Jan 9, 2009
    358
    3
    Regenerative breaking is just to keep your DC Bus voltage to a level that won't explode your bus caps/power switches.

    Electromechanical braking is like 'dynamic braking', in that if power goes out it engages to add torque to the shaft. Imagine a motor holding a weight against gravity. If power is lost it would fly to the floor. Regenerative braking won't do anything in this case. Dynamic braking shorts all phases through power resistors to burn generated energy from this motion however it only provides 'resistance' and not a 'stopping' force. Ideally, you should NOT be counting on your electromechanical brake for emergency stopping. It is just there to 'hold' when power is off.
     
  9. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    I've worked on several equipment with regenerative breaking. All it did was throw a relay across the motor, making it hard to turn (also disconnecting power in the process). The one I have in mind is a 5000 G centrifuge for microelectronic hybrids. We also used it for the small arena in our battlebot hazard.

    I suspect we'll have to agree to disagree on this one.
     
  10. Skeebopstop

    Active Member

    Jan 9, 2009
    358
    3
    What I just called 'dynamic braking' is what some call 'regenerative braking'. There is a clear distinction in my field though as I design servo drives.

    Regardless, yes you are correct, there are certain situations where the 'regenerative brake' can be used as a brake. One such in our situation is an emergency stop where the DC Bus (600V typically) is disconnected, the IPM's (intelligent power module) high side IGBTs are turned full on and the regenerative brake turned full on. This in effect completely discharges the BUS and continues to do so until 'all' energy is soaked out of the motor.
     
  11. tbeaver

    Thread Starter New Member

    Oct 4, 2009
    6
    0
    This buggy had a dynamic brake on it from the factory. As far as I can tell they used what looked like a solenoid or maybe it was a relay to engage it. The buggy also has a front and rear brake so we'ere not relaying on only the dynamic brake. I was just wondering how to wire the #'s 1-2 wire from the drawing in the link i supplied.

    Thanks for helping.
    tbeaver
     
  12. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    Just curious, what do you think the stop limit is for? My impression is that it is for automation, basically a generic switch to enhance the controllers usefulness. I don't think it would have an application in a moving vehicle (unless it's inside the bumper :p ).

    How much did you spend for the controller?

    I'll study it a bit and see what I can make of it. It looks like a good piece of electronics.

    As for noob questions, we live for them. I find I learn a lot re-examining things I knew for a fact now and then. I think Will Roger once said, "It's not what folks know that get them in trouble, it's what they know that ain't so.".
     
  13. russ_hensel

    Well-Known Member

    Jan 11, 2009
    818
    47
    Sometimes regenerative breaking is done to recapture kenetic energy and use it to charge a device ( battery, cap? ) for later use. A true dead short dumps the energy as heat in the motor.
     
  14. tibbles

    Active Member

    Jun 27, 2008
    249
    3
    "How much did you spend for the controller?"
    bill, i once priced one of these up in the uk-get ready for a shock
     
  15. Skeebopstop

    Active Member

    Jan 9, 2009
    358
    3
    Regenerative power supplies are the way of the future. Capacitor banks are much better even than regen brakes but are still big and bulky but at least you store the energy up, but for big megawatt machines, rather than burn it as heat in resistor banks the size of your bed, synch it to the mains via an inverter and push it back into the grid.
     
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