Patient Lifter SARA 3000

Discussion in 'General Electronics Chat' started by repairs online, Sep 17, 2012.

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  1. repairs online

    Thread Starter New Member

    Nov 3, 2007
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    Looking for schematics to patient lifter, model SARA 3000.

    Also suggestions why lift motor would work one way but not the other. To be more specific, if the power wires are connected to the the motor in such a way where the shaft can be extended, it will not retract. To make it retract, requires reversing the power wires and vice versa. Have checked toggle switch, and handset buttons, no problems.

    There are a total of 8 mosfets on the main board, all type IRLZ44N. The base leg motor works ok but not the lift motor. All mosfets check out ok.
     
  2. Adamf001

    Member

    Sep 5, 2011
    67
    2
    to make a motor turn one way and then another you need a H-bridge,

    [​IMG]
     
  3. repairs online

    Thread Starter New Member

    Nov 3, 2007
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    In its normal operation, yes, but not necessarily, the same effect can also be accomplished by reversing the power leads. And this is exactly what is taking place with this ARJO-HUNTLEIGH Patient Lift machine, model SARA 3000.

    http://www.arjohuntleigh.com/Product.asp?pagenumber=243&Product_Id=20&ProductCategory_Id=13

    If all 4 Mosfets in the H-Bridge were working OK, pressing a toggle switch one way should activate, say, extend the shaft of the actuator motor AND pressing the switch the other way should retract the shaft.

    But this was not happening. so, to reverse the current or cause the current to go the opposite way, the power leads had to reversed.

    This is a microcomputer based, PIC 16C77, full solid state, NO RELAYS, Patient Lifter.

    Surely, in this vast forum, someone must have the schematics to this lifting machine.
     
    Last edited: Oct 4, 2012
  4. MrChips

    Moderator

    Oct 2, 2009
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    There are limit switches to stop the motor when one extreme position is reached but still allow the motor to reverse.
    Check that all limit switches are working correctly.
     
  5. repairs online

    Thread Starter New Member

    Nov 3, 2007
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    In fact, during testing, the actuator motor was extended to its limit and stopped automatically. To reverse it, I had to reverse the power leads.
     
  6. cork_ie

    Member

    Oct 8, 2011
    348
    58
    Sounds like some kind of interlock problem. If you cannot retract the motor, without reversing the polarity, it is the inner (fully retracted) limit switch you need to look at.

    There will be limit switches of some sort at both stop positions or alternatively current sensing on stops, which doesn't seem to apply in this instance.
     
  7. DMahalko

    Senior Member

    Oct 5, 2008
    175
    14
    This is a medical device with the potential to injure or kill a frail hospital patient, so there are no doubt safety precautions installed to prevent the device from malfunctioning in a harmful manner.

    Access to the circuit schematics are probably restricted by the manufacturer for liability reasons. Is your business certified by the manufacturer to do this kind of repair work?

    It is odd that a care provider would be using an unlicensed repair service, since they will get sued if you fix it wrong and the device ends up hurting a bedridden patient.



    But anyway, regardless regulations and rules, there is probably a safety lockout trigger, that is preventing normal operation. Probably a stuck or jammed limit/safety switch somewhere.

    It can be as simple as having a random object caught in some nook that is keeping a limit switch constantly activated.
     
  8. repairs online

    Thread Starter New Member

    Nov 3, 2007
    38
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    I thought for a moment, I was in a forum of solicitors, please, keep it technical.

    All limit switches work 100%, no problems whatsoever. Put limit switches completely out of your mind.

    And in looking for technical assistance, ONLY, on this issue, I was expecting responces from those members which some know-how on these problems.

    Suggestions are also welcomed. As explaned, the circuit is purely solid state, no relays involved, and quite complicated to trace signal flow. You could end up chasing your tail, one reason, 99% surface mount and double sided.

    As everybody knows service manuals are copyright but that does not prevent anyone providing a copy for study purposes.
     
  9. MrChips

    Moderator

    Oct 2, 2009
    12,440
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    I have to disagree with you on three counts.

    1) Safety is an important issue. In light of this, this thread will be closed.

    2) With regards to limit switches, one of the rules of trouble shooting is you do not rule out anything.

    3) This forum is provided through the generosity of many, the owners, moderators and members. If you don't like the advice given, go someplace else.
     
  10. debe

    Well-Known Member

    Sep 21, 2010
    946
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    You will find Workshop manuals are probably in house only, will never see the light of day. Only option is reverse engineer.
     
  11. DMahalko

    Senior Member

    Oct 5, 2008
    175
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  12. repairs online

    Thread Starter New Member

    Nov 3, 2007
    38
    0
    The point made was to restrict the information to TECHNICAL assistance ONLY.

    Had I sought legal opinion or advice on the legal ramifications, I would have asked so.

    Apparently, some members, for reason unknown, presumably, because of their own shortcomings or been the fatherly or motherly type give advice not related to the question(s) been asked.

    On the other hand,their attitude may appear condescending.

    So, to iron the board out, I thought I should make myself very clear.

    Do you understand that Mr Chips.

    You responded first with a probable cause involving the limit switches. Thank you for your response BUT without sounding ungrateful, if have you read my postings more carefully and had extended experience in actuator motors and their electronics, a limit switch could not have been causing the problem.

    And to reinforce the point -no limit switch problem, I said so.

    DMahalko also responded, but I think his prime motive was to offer legal advice. Nothing else to say, he repeated what you said, in his own way.

    So, to stop the discussion diverging into an area of no interest to me or to the point raised by the original post. I thought, I should make it clear what the post was all about.
     
  13. repairs online

    Thread Starter New Member

    Nov 3, 2007
    38
    0
    Well, I did approach ARJO, but contrary to what is been said in the manual, although, I have not seen it, they refused to release it. In fact, even sell spare parts.

    One had to buy the hole board, running into hundreds of $$$$.



    ........ but again, I am not in the UK, perhaps, they have different policies.
     
    Last edited: Oct 5, 2012
  14. cork_ie

    Member

    Oct 8, 2011
    348
    58
    Sorry, but I don't think anyone with this kind of attitude deserves help.
     
  15. paulktreg

    Distinguished Member

    Jun 2, 2008
    611
    120
    I have yet to come across the Sara 3000 but in my experience circuit diagrams aren't readily available these days unless you've done an "official" training course. You could ask the owner of the equipment to request the information, they are entitled to it in the UK, but even then it may be fight. Gone are the days of fault finding to component level in the medical field and you may have to buy a new board.

    "@MrChips - 1) Safety is an important issue. In light of this, this thread will be closed." ... when exactly and when were you given that power?
     
    Last edited: Oct 5, 2012
  16. DMahalko

    Senior Member

    Oct 5, 2008
    175
    14
    If you're coming to this board posting about some device and providing very little background info on what you're doing or why, then it is within my right to bring up all the details that can be found on the 'net about whatever the device is.

    Medical equipment is highly regulated due to all the liability issues, and it's a valid point to talk about safety and hazards.


    I know I don't want some random high school kid working on the X-ray machine at the local hospital when I go in for testing, nor do I want some jury-rigged nursing assistance lifting device used on me by the hospital if I'm in for surgery.

    Nobody else should have to be in that situation either, but helping you hack this device will probably put someone in that situation. Helping you with your circuit hacking problem is less important than looking out for the welfare of the people your hacked device will probably end up being used on.


    And besides, if you had went through ARJO's training program and were certified by the company as an authorized repair technician for their products, we probably wouldn't be having this forum discussion at all.
     
  17. repairs online

    Thread Starter New Member

    Nov 3, 2007
    38
    0
    .....DMahalko, please, change frequency.

    But, you raised an important point about ARJO's training course, I did ask an ARJO trained technician, and all he said, there is no such thing.

    All we told to do is to change the board, and in this particular case, there are only 2 boards, if not one then the other or both. Anyone with rudimentary knowledge can tackle it.

    Why, you may ask, because it makes money for the company.

    Further more, they are not required to be qualified to do repairs to component level, like I am.

    In assisting someone with a schematic can not be called hacking. Most companies sell them as spares. And in some countries, these companies are required to do so by law.


    Of course, you may have a different opinion. Sure, you may a raise your opinion on an issue not directly relating to the substance of post, however, if the the author of the post is not interested, then, .... you must stop offering such advice.

    You and I do not know each other, for all I know, we may not be leaving in the same country.

    Further, you may not make wild accusations or implications about the competency of other members.

    If you want to raise a post on legal issues, do so, but under your own post, and not in other members' posts, especially, when it has been, clearly, stated not to do so.

    Now, have you got a schematic to send but having second thoughts, don't worry, be happy. Forget about the second thoughts, send the schematic.
     
  18. JoeJester

    AAC Fanatic!

    Apr 26, 2005
    3,373
    1,159
    I'll assume the "controller" reverses the polarity to the "lift". Knowing that the motor is a DC motor, I can assume the controller more than likely has an H-bridge to reverse the polarity.

    Now, if you don't like the manufacturer's way of doing business (replacing boards), then I guess you will assume whatever liability issues associated with your repairs. This does not mean the members here will assist you in the manner you wish.

    If you don't want to purchase the service manual (or if it's not available), you can only reverse engineer it. I doubt many members here would have that schematic readily available and I doubt they would share it if they had it.

    I do think the moderators should shut down this thread.
     
  19. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    Tecnical yes, Safety oriented, even more so. Do not confuse the two, this is primarily a teaching site, as well as a resource to consult other knowledgable people. You can not pick and choose what parts you like, if in the opinion of any of the moderators or administrators this is not a safe thread then it will be closed.

    Safety is first. Having just read the second page I am closing this thread until the moderators (I am one of several) decide whether to open it back up.
     
  20. Georacer

    Moderator

    Nov 25, 2009
    5,142
    1,266
    This thread will remain closed permanently, due to newer posts by the OP.
     
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