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I have to build a "usage status indicator" for a syringe. Conditions are as follow. 1. if syringe is used for 3 times, it should show some indication. 2. if syringe is used less than 3 times, it should show some other indication. can any one suggest some ideas?

ashish
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    If you want to use electronics to do it, you're going to have to have a power supply. Fairy dust is not a viable power source. – Matt Young Dec 22 '14 at 14:19
  • Depending how much control you have over the syringe design you can probably do a mechanical implementation... But yes, for electronics of any sort, you will need a power source. – Jarrod Christman Dec 22 '14 at 14:20
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    You have asked essentially the same question three times now, with minor variations and omitting important design constraints. You have had answers, but apparently they did not meet your constraints. If there are price constraints, size constraints, environmental constraints, state them. Here you don't even say what "used" means in this context : does it mean emptied and refilled, or does it mean some quantity (e.g. 1ml) has been dispensed. So how can anyone possibly answer? Now you say it's for a syringe ... if this is a medical application that changes the answer A LOT! –  Dec 22 '14 at 14:30
  • This is a really big design problem -- not only the bit about the power supply, but a reliable way of tracking "use" – Scott Seidman Dec 22 '14 at 14:35
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    Idea #1: get a power supply. – Greg d'Eon Dec 22 '14 at 14:37
  • @MattYoung The sesame street program I'm watching with my little one this morning begs to differ with you. – Some Hardware Guy Dec 22 '14 at 14:42
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    A few years ago some guys at Northeastern figured out if you have tiny disc with nano channels in it, and you force water through it in a syringe then you can produce enough electricity to light an LED. So maybe it's possible but it's going to take a heck of a lot of R&D. Can't find a link to original article. – Some Hardware Guy Dec 22 '14 at 14:46
  • @SomeHardwareGuy Are you sure that's not Sensimilla Street? – Majenko Dec 22 '14 at 15:00
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    Button cell + mechanical switch sensor + ASIC + LCD display is certainly viable if you don't mind the cost and MOQ. A syringe probably costs pennies to make so the cost is going to be multiplied. It might be cheaper to throw the syringes away every time. – Spehro Pefhany Dec 22 '14 at 15:38

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Electronics is no magic, it is about forcing electrons to go wherever we want them to go - but we need power supplies for that (even though they might be very low power).

It all depends on how flexible your requirement is and what you meant by "power supply".

Without thinking about it too much, I can see two options:

1) You really don't want any sort of battery or power supply. I would personally use one of those mechanical push counters (e.g.) that would count every time the shoulder of the serynge is lowered (that you can strip apart), or design some homemade simple mechanical mechanism based on racks and gears instead if it's too bulky. Note that this would not be the right StackExchange to post on.

2) Use a button battery like in real time clocks/motherboards or watches, and power a simple limit switch counter with that. Yours to tell whether you want a battery indicator as well (separate IC+LED).

Note that if it's a product for the medical market, you will need to think things through a lot more, based on the certifications you will have to comply to - so I'd say start by researching that. I know EC marking for example (for european products) has a Medical directive.

Mister Mystère
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