Long jumper wires, how big of an issue?

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  • Hello!

    My first post and my first Espruino board, exciting times!

    The project I have picked is to create a motion sensing based counter for our table football that will be posting to a PHP live app running on a TV. I have got the board and 2 motion sensors to start with. Obviously each motion sensor needs to be in each goal, which means that each of the jumper wires will need to be at least 60cm long. Is that an issue? Will I see any loses?

    Also If I create an API, can I easily do a POST request with parameters included? The plan for future is to attach NFC reader so the table will know who is playing, which means I will be sending a lot of data to the PHP app (score, scorer, average time between goals etc).



  • Long wire will increase resistance and inductance. It depends on the kind of signal you are dealing with if it matters or not. Unless you are doing some high-speed digital I expect it should be fine. If you want to be really careful, use thicker wire.

  • It all depends on what kind of motion sensor you're using - but most reasonable ways to sense a goal won't care. If you were trying to do digital comms over that distance, you might need to think about it, but I get the idea that you're just doing something that'll pulse a pin when it seems something - that'll be no problem. SPI or I2C over that distance would probably work, but you'd have to start thinking about it.

    Yes, you can do POST requests, no problem: http://www.espruino.com/Reference#l_http­_request

  • Hi :) I think your answer is already answered but I just wanted to urge you to create a thread for your project over at the Projects sub forum!

    Have you decided on a sensor yet?

  • Hi, as others have said you'll be absolutely fine for most signals. Even on things like SPI and I2C, you can control the clock speed of the signal so if you have problems you can just lower it.

    For sensing when the ball goes through the goal, you could use an LED and a light sensor so you'd know when something had got in the way of the LED's light. You could even use Infrared so you couldn't see it.

    Something like that would work fine over longer distances. There's not much current drawn either, so the thickness of wires wouldn't be an issue,

  • Hey all,

    Wow, thanks for all the input!

    This is the sensor I bought > http://www.ebay.co.uk/itm/Pyroelectric-I­R-Infrared-PIR-Motion-Sensor-Detector-Mo­dule-HC-SR501-Arduino-New-/131305435900?­pt=UK_Computing_Other_Computing_Networki­ng&hash=item1e9269f2fc

    So I understand there should be no problem when connected on a 50 - 60 cm wire? All it needs to do is really send a signal when it senses the ball and then wait atleast 4 - 5 sec (just a timeout) before it can start sensing again.

    Would connecting multiple 20cm male to female wires do the job, or should I look for one single wire?

    Thanks so much!


  • Hi,

    Yes, that sensor would work fine with longer wires (it sends ~2 second pulses when it detects movement IIRC). While you could join a bunch of jumper wires and it'd work I'd suggest you make longer ones (because chances are that with all the shaking one of the connectors will fall apart at some point!).

    However I do have some bad news I'm afraid. Those Pyroelectric motion sensors work by detecting changes in heat - so they'll detect humans and animals, but I'm afraid it's really unlikely that they'll detect balls :(

    You could use something like this but you'd want to cut it in half and then mount each half facing each other. If you follow the link on there to eBay you can even buy a little module (you don't need it) but it's got a light and a potentiometer so you can easily test it and tweak the sensitivity (again, you'd have to unsolder the LED or detector and then move them to the other side of the goal).

  • Instead of cutting that sensor in half, try using it like a laser beam sensor...attach a small mirror to the other side of the goal, aim the sensor at the mirror and then detect when the ball breaks the beam. Might work.

    eh...I just looked at the datasheet. Distance to reflector needs to be about 14mm or less. If you cut it in half, you'd get about 28mm, just over an inch, probably not enough...

    Unless... the ball is shiny enough to reflect back to the sensor. You could put a sensor on each side of the goal. I don't think you can know what works until you try it.

  • Distance to reflector needs to be about 14mm or less.

    Didn't see that - but if it's reflected by a mirror (or TX is pointing at RX) then I think it would be substantially better than that.

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Long jumper wires, how big of an issue?

Posted by Avatar for Foxhoundn @Foxhoundn