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Conditioning Electronics Problem

  1. Aug 28, 2012 #1
    Please forgive me if I am posting this in the incorrect forum, and if I am, could you be so kind and point me in the correct direction?

    I work for a Engineering Manufacturing company located in California, we are contracted with various military, medical, mining companies and we have ran into a issue with one of our products.

    We have designed a USB (Game or Cursor) or Bus and Digital Interface Multi-Channel Programmable Signal Conditioning and System Interface Electronics.

    It is used in a mouse that controls heavy mining equipment under ground, the operating Voltage Range is 2.0V to 5.5V, a lot of these mice are coming back to us for repair (They are not cheap $2,000+ per one, and replacing them under warranty gets costly, hence my question). We are afraid that whoever is connecting the mouse to the mining equipment is operating it over the maximum of 5.5V range. My question: Is is there a way to check if in fact the the Voltage was exceeded its maximum range? Any help would be much appreciated.
  2. jcsd
  3. Aug 28, 2012 #2


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    Hi DawidM. Welcome to Physics Forums.

    If many of your customers are damaging the apparatus, perhaps you should modify it to withstand the conditions it is experiencing? If something more robust is what the customers are demonstrating they need, then isn't it good business to deliver what the customer wants?

    Whoever is at fault, surely your company would want to avoid earning a reputation for not standing behind a product that you acknowledge is prone to damage in the environment where it is apparently being marketed, and where it has become popular with users?

    I expect you could add a small circuit to your product that permanently damages a component to register that the mouse has been subject to a voltage exceeding its designed range, but that seems to be going about it the wrong way. If you can't stand behind the warranty, maybe the best business option would be to discontinue the product. It will only be earning you a black mark in the market if you leave a trail of angry and dissatisfied customers.

    There's a need for a more robust mouse, so why not jump in and be the first to meet that need. :smile:
    Last edited: Aug 28, 2012
  4. Aug 28, 2012 #3

    Thank you for your reply, and it is nice to be here. This particular apparatus is used only by one customer. I completely agree with the statement of delivering what the customer wants. This is where the problem arises. That apparatus is build to the exact specifications the customer had provided us with. The reason why the maximum operating voltage range is set at 5.5V is for safety measures, if for some reason there is a emergency with the machine ex fire the apparatus will shut down preventing the part it controls from swinging uncontrollably.

    We stand behind our product 100%, and we honor the warranty we provide with it. If the product fails to operate to it's specifications due to a manufacturing defect we will replace it without a problem. When the instructions on how to install, connect and operate the product are not followed and cause permanent, irreversible damage to the unit, we do not believe we should be at fault and responsible for the cost of replacing that product. Keep in mind these machines are worth hundreds of thousands of dollars, if not millions. If my laptop manufacturer warns me that irreversible damage may occur if I use incorrect AC adapter and I ignore it and result with a "dead" laptop, should I in return get a new laptop?

    That's a great idea, I will pitch it to my superiors. Thank you for that. Like I said, we will honor the warranty if the internal component fails due to faulty part, improper wiring, in general a defective part that had escaped our facility (we test all units throughout the manufacturing process and right before shipment). We want to keep our customers happy and stay profitable, just like any company out there but not lose profits because the instructions were not followed.

    Thank you very much for your help and your input on this matter, your opinion really matters and did not go unnoticed.
  5. Aug 28, 2012 #4
    Keep in mind these machines are worth hundreds of thousands of dollars, if not millions.

    If I was selling a million dollar machine, I would damn well provide a mouse that didn't fail no matter what the user did to it.
  6. Aug 28, 2012 #5


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    If they are restricted to 5.5V for safety reasons then applying a greater voltage is in violation of their rules. You need a voltage sensitive interlock, if anything over 5.5V is applied the machine should lock out until a safe voltage is applied.
  7. Aug 29, 2012 #6
    @Carl Pugh

    Everything has it's limits, not trying to sell our product but here are some key points:
    -Solid State Welded (hermetically sealed)
    -Solid Stainless Steel construction
    -Sensors and input devices with no moving or rubbing parts for survivability and performance
    -Meets/exceeds EMI/RFI susceptibility requirements
    -Operational Life is rated at 10,000,000+ cycles
    -Shock +50G
    -Water resistance up to 1 meter for 2 hours
    Vibration 10-55Hz at 0.6DA, 55-200Hz at 10G

    It is a mouse that will survive almost anything, if a few ton machine runs over it, off course it will break, if the user starts sticking a screw driver into it he will mess something up, if somehow he cuts the cable it's done. If you ask me, I believe we have met the requirements of making a good quality product.The issue we are having is not with the operator but the individual who is not following our instructions on installing this unit and ruins it and expecting a free replacement and we get stuck with a expensive paper weight and sending them a brand new unit.


    You are correct. Our warranty is simple. If it is manufacturing defect we will replace it with no questions asked. If it is customer incurred damage warranty is void. Proving that greater voltage was applied to it is why I have posted my question here. I will look into the interlock tomorrow at work. I appreciate your help, thank you.
  8. Aug 29, 2012 #7
    This problem has the possibility of blowing up in your face.
    You should let your supervisor know how many mice have come back. Your supervisor should tell you what to do.
    Your supervisor should let sales know that there is a problem.
    Your supervisor should go to whoever designed/made the mouse and have them determine the cause of the failure.
  9. Aug 29, 2012 #8
    Is it possible for some equipment fault to cause high voltage/current transients? Did you have your mouse and equipment validated with some kind of testing that would test for over-voltage conditions or could cause the equipment its connected to to fail in that way?
  10. Aug 30, 2012 #9

    jim hardy

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    how many wires are on it?

    when it is plugged and unplugged, do you know in what sequence the pins in the connector make & break?

    It is very possible that something sees more than normal voltage or current because of , let us just say for sake of an example - while it's getting plugged into a gizmo its filter capacitor charging current returns through a signal input line instead of the power supply return line because of the order in which the pins make contact. This will be almost random depending on how the customer holds the plug as he connects it,,, Left handed technicians may get by fine while right handed ones kill mice.

    That's just a guess. But most connector suppliers offer a longer pin to solve just that problem.

    A 5.5 volt zener in series with a fuse would be a telltale.

    Were it mine, i'd look at LDO automotive voltage regulators - they are protected against both overvoltage and reverse polarity for just these reasons. National LM2936 for example...(oops now they're TI)

    old jim
  11. Sep 12, 2012 #10
    I agree with JH - I was thinking just a Zener - it will protect the mouse, and if you get them back with blown Zeners - and damaged internal circuits then you know for sure the power supply providing the 5.5 V is the issue. Then That issue should be addressed. Any field wiring in industrial applications is suspect and should have surge protection like this and other protections.

    BTW - in the field, is the wiring from the 5.5V supply to the mouse very long? If so - when being plugged in - or more realistically unplugged the mouse may be seeing an inductive kick - the zener will help with this possibly as well.
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