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Meder Reed Switch, Digmesa Flow Meter & Arduino?

Former Member

Hi,

 

Complete arduino newb and want to use this reed switch I already have MK04 Reed Sensors  It doesn't look like they make the exact model anymore (MK4-1A71-BV10102), but its a 1A/Form A with 2 wires.  Can I connect two wire sensors to Arduino or have to be 3 wires?  I think maybe I can do it this way, but don't want to fry anything.  bildr » Simple Temperature With Thermistor + Arduino  Or maybe don't connect 5v because magnet generates power?

 

Also have this flow meter http://www.digmesa.com/wp-content/uploads/2014/01/FLOW-SENSOR-FHKSC.pdf  Can I do it like this?  Seeedstudio Forum • View topic - Tutorial: Reading Water Flow rate with Water Flow Sensor  What I am not sure is the voltage, it says it is 20v or 24v.  I don't know how that affects things since Arduino 5v.

 

Thanks for any help!

  • If you are using a two wire reed switch you can connect it like this:

    image

  • Without looking at the datasheet, the reed switches will come in different forms.  Normally Closed (NC) or Normally Open (NO), or a Com and both NO and NC.  So depending on the one you are using, you will want to use either a pull up resistor or pull down.  Depending on how you hook the wires, to +5vdc or GND, if you connect one side to +5vdc on the NO side of the switch, used a pull down on the other side to a Digital Pin in.  This will keep the Digital pin from floating and can give you a wrong indication.  You will have to play with the NO or NC type of switch for best results.  The Magnet will wither open or close the Reed switch depending on what you are using.  This will hold true for any type of switched input.  Your pull up or pull down can be 10K ohm for larger.  Play with it until you have the best results.

     

    Regards,

     

    Dave M.

  • With respect to your flow meter, page 3 of he following document may help you: http://www.mpja.com/download/31430hd.pdf

  • The reed switch is just that a switch, activated by a nearby magnet, treat it like a button on an arduino input and you should be fine as long as the wires are not too long or near hi voltage interference

     

     

     

    The thermistor / resistor pair you show in the other diagram should work by simply feeding the junction of the two into the analog input of the Arduino, A5 for instance

     

     

     

    The reed switch is not a magnet and has no coils to generate power, it is simply a switch contact that closes when a magnetic field is close enough to make the contacts pull together (Or separate depending on the model)

     

     

     

    The flow sensor has two issues,

     

    1.       It runs on 20 or 24V or so it seems, you most lightly won’t have this available to you easily without buying an adapter

     

    2.       It does not specify the output pulse, this could be a relay contact closure, a hall effect sensor or something completely different so until you know it is tough to advise, I suggest hooking it up to a meter (Not Arduino) and powering it up to see what it gives out, if you can find more product details that would help us advise you

     

    Technically you can do something similar to the example linked in but your interface would be different depending on the output and actual supply of the flow meter

  • in reply to gadget.iom

    I would suggest having the resistor to + 5V and the reed switch to ground, this way if the code programs the pin as an output and LOW, you’re not trying to ground the 5V rail without current limit and blow the arduino pin if the read switch is closed

     

     

     

    (The Arduino has limiting built in to prevent sourcing too much current in the event the pin is grounded by the switch)

     

     

     

    Just a different option, in most cases you will be ok

     

     

     

    Peter

  • in reply to gadget.iom

    Nice find Paul

     

    Looks like you can run this in the same way as the sparkfun with only a 5V supply

     

    Peter

  • in reply to gadget.iom

    Yeah, that's great I didn't find that one.  I think I understand, if I use a capacitor, then I can go down to 5v.  Thanks!!!

  • Wow! Thanks for all the replies, I think I can work through it.  Gotta order the arduino, but waiting until I knew if I could use what I already had.  May have some more questions down the road, but thanks a bunch you guys, I really appreciate it.  It's for espresso machine I am building here if you want to check it out...Homeroasters.org - Discussion Forum: Starbucks (Saeco) Sirena