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Running 12V Micropump w/ BS2???? — Parallax Forums

Running 12V Micropump w/ BS2????

jpalme5jpalme5 Posts: 5
edited 2007-03-11 03:12 in BASIC Stamp
This is my first post so I will explain what myself and my senior design project is. My name is Jason Palmer and I am a senior in Biological Engineering. I am building a Dual BioSensor for the detection of E. coli in water. Various chemicals will be used to react with the E. coli which will cause an oxygen reaction. The amount of oxygen released will be detected by a dissolved oxygen sensor that is separate from the BS2. I will also be detecting a change in color of the chemicals via light absorption with a TSL120 light sensor and a 420nm LED.

I am using four 150SP micropumps from BioChem Valve. They run on 12V DC with 2.6 watts of power. The spec sheet can be found here. A 12V rechargeable will be used as a power source. I am using TIP120 transistors for each pump.

Currently I am in the building phase and I am using a BS2 Homework board to test everything out (ease of use with breadboard). For the final setup I plan to use a BS2 Super Carrier Board so that I can solder all of the connections.

Now to my questions.

1) For the TIP120 the base will be connected to the BS2 output with a 1K resistor in between. For the collector, does the ground hook up to the negative terminal of the battery or to the ground of the BS2? I will connect all the pumps to a single ground wire.

2) How do I wire the emitter into the with the + terminal of the battery and the BS2? What do I do with the second wire of the micropump?

3) I want to use a the 12V battery to power the pumps and the BS2 Super Carrier Board. Can I just wire the power line into the board since it already has a voltage regulator or do I need to add a resistor or capacitor? Would it be easier to just use a 9V battery that plugs into the board to power it instead of the 12V?

4) Is there anything in the wiring that I have overlooked that is needed or would help the system perform better? Any suggestions for the other components?

Sorry if this is a bunch of stuff. This is the first time I have fooled with a BS2 and I do not know much about electrical components, so I am learning on the fly.

THANKS FOR THE HELP.

Comments

  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2007-03-11 00:29
    Hello,

    Actually for each TIP120 the emitter will go to ground. The negative side of the motor will go to the collector. The positive side of the motor will go to the common power supply for the motors which should probably be different from the BASIC Stamp supply depending on its specs. The NPN transistor should be switching the negative side of each motor. I hope this helps. Take care.

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    Chris Savage
    Parallax Tech Support
  • FranklinFranklin Posts: 4,747
    edited 2007-03-11 00:30
    1) you should have a common ground for all electronic devices, this gives the devices a common reference point.
    2) The emmiter goes to the motor - then the motor + goes to the battery +
    3) 12v dc should be OK for the stamp, it will only use what it needs. 5-15V is OK.
    4) attach the schematic and maybe we could tell you.

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    - Stephen
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2007-03-11 00:36
    Franklin said...(trimmed)
    2) The emmiter goes to the motor - then the motor + goes to the battery +
    Franklin...The TIP120 is an NPN (Darlington) transistor...The Emitter should be to the Ground side of things and the collector should be switching the negative side of the motor.

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    Chris Savage
    Parallax Tech Support
  • FranklinFranklin Posts: 4,747
    edited 2007-03-11 00:47
    Chris, sorry, in the future I'll try to be more generic in my posts since in most cases when I use something I hae to look up it's specs and I was relying on jpalme5's description for the connection.

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    - Stephen
  • jpalme5jpalme5 Posts: 5
    edited 2007-03-11 01:02
    So for the common ground, I should have the emitter from the all the TIP120's and the VSS from the Super Carrier Board connected to a single wire. This wire, or set of connections, would then connect to the negative terminal of the 12V battery which would complete the circuit for the entire system.

    Is this correct?

    Sorry for the novice questions..........
  • Tracy AllenTracy Allen Posts: 6,664
    edited 2007-03-11 03:01
    It is better to have one set of wires from battery terminals to the carrier board/stamp, and another set of wires from the battery terminals to the pumps and TIP120s. That is, keep the power for the pumps isolated from the more sensitive controller electronics. It may help to add a capacitor in parallel with the battery, something like 220 microfarads. Smaller wires can carry the control voltage over to the base terminals of the TIP120s, but the transistor emitter and collector are part of the higher current path. It may also be wise to install a diode across each pump motor, with the cathode pointing toward the +12 side; that is to absorb spikes of voltage that can occur when current to a motor is shut off.

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    Tracy Allen
    www.emesystems.com
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2007-03-11 03:12
    Attached is a simple transistor control schematic for a motor...This will also work for the TIP120 Darlington you have. But Tracy is right...Perhaps you should connect all the power stuff together at one end (including the transistors) and just run the control wires (including a common ground from the BASIC Stamp board) to the power system. Take care.

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    Chris Savage
    Parallax Tech Support
    Driver_Motor_NPN.JPG
    320 x 247 - 6K
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