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Topic: Circuit Confirmation (Read 757 times) previous topic - next topic

Arbiter472

Hi guys,

I am designing a paintball marker and have ironed out this circuit design. I just want to be sure if this is likely to work, or where it should be altered/improved. I am new to circuit design so chances are there is a flaw or two, hence this post.

Below is the circuit design of my project so far.



The push buttons to be used for menu and safety are using 220 ohm pull down resistors. The MOSFET uses a 10k ohm pull down between the gate and the ground to prevent floating of the Gate when its not activated -is this 10k resistor adequate or should I rather use another value?

The Solenoid gets its power from the 5v pin of the Nano. This is where I had a bout of self questioning. Should I rather connect the Solenoid directly to the + of the 9v battery with a resistor to bring the current down, or is leaving it connected to the 5v pin of the Nano ok?

The diode I incorporated to prevent the back flow of current when the solenoid is no longer activated from damaging the MOSFET and other components.


If you could please let me know if the above will work or where I can improve the design, I'd really appreciate it.
Thanks in advance guys.

DrDiettrich

Please supply a circuit diagram.

A 9V block battery is not a good choice for driving a solenoid, use a more powerful battery/supply.

CrossRoads

Don't drive solenoid from the Nano's regulator, you'll smoke the regulator, it's not heatsinked well enough to provide more than maybe 100, 150mA.
http://www.digikey.com/product-detail/en/texas-instruments/UA78M05CDCYR/296-12290-1-ND/416584

Buttons: wire them to connect the pin to Gnd when pressed, and use the internal pullup resistors on the '328P chip instead:
Code: [Select]

pinMode (pinX, INPUT_PULLUP);
and then
if (digitalRead(pinX) == LOW){
// button pressed, do something
}
or
buttonStateX = digitalRead(pinX);
if (buttonStateX == LOW){
// button pressed, do something
}

10K pulldown is fine to keep the MOSFET gate from floating. Diode is good.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

Arbiter472

Please supply a circuit diagram.

A 9V block battery is not a good choice for driving a solenoid, use a more powerful battery/supply.
The solenoid i am using is designed for paintball and not the external piston types, its an air solenoid designed to operate at around 90-100 psi and usually the board, solenoid and other components run off 4x 1.2v 750mAh batteries in series. Would you recommend 4x 1.3v AA batteries in series instead?

CrossRoads

You may want to use boost converter from pololu.com for example so that solid 5V is available to the Arduino while the air solenoid takes big chunks of current to fire. Should keep the Arduino from resetting when the voltage drops.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

Arbiter472

Don't drive solenoid from the Nano's regulator, you'll smoke the regulator, it's not heatsinked well enough to provide more than maybe 100, 150mA.
http://www.digikey.com/product-detail/en/texas-instruments/UA78M05CDCYR/296-12290-1-ND/416584

Buttons: wire them to connect the pin to Gnd when pressed, and use the internal pullup resistors on the '328P chip instead:
Code: [Select]

pinMode (pinX, INPUT_PULLUP);
and then
if (digitalRead(pinX) == LOW){
// button pressed, do something
}
or
buttonStateX = digitalRead(pinX);
if (buttonStateX == LOW){
// button pressed, do something
}

10K pulldown is fine to keep the MOSFET gate from floating. Diode is good.
Thank you for the post hey, so if i understand you correctly, you would suggust i wire the solenoid directly to the battery pack with a regulator and possibly a resistor (depending on regulator -i live in a place where there is limited choice available) to power it?

I have read up about wiring buttons using a pull-up, but didn't quite understand why that would be better than the pull down. Could you by any chance shed some light on that logic for me please?


CrossRoads

Pullup better than pulldown as it's built into the processor so an external resistor does not need to be added.
If there are really long wires from the button to the processor than an external pullup might be needed anyway to overcome any noise picked up on the wires.

I don't think solenoid needs a regulator - just connect the 4.8V to 5.2V power to solenoid "+", "-" to MOSFET, let MOSFET make the Gnd connection, as you drew it. The solenoid coil provides the DC resistance to current flow, no extra resistor is needed.

I would only suggest the boost regulator to power the arduino so it doesn't reset when the solenoid fires.

Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

Arbiter472

I have been doing a lot of reading on powering Arduino's and seen many different ideas and approaches. I have an idea of the way forward I wish to take but want to ensure I don't mess up my board in the long run.

Almost all paintball markers run off a 9v battery and do so pretty well, but I guess that would be attributed to the design of the boards and regulators etc. As you can see in the diagram above, I used a 9v Battery pack to power the board, which I have changed from the Nano to the Micro as the Nano that was supplied to me was shipped with a counterfeit FTDI serial converter chip which FTDI no longer supports.

I have seen posts of 3-4x AA batteries being more efficient when compared to 9v ones. That being said, what would be your recommendations on this? I am willing to go either way so long as it will work. In terms of regulators, I have seem many different types online, but it seems the consensus is on the boosted 5v output regulators.

So my question is, which of the following is best?
1) Using a 9v battery through the 5v Boost regulator where the board and Solenoid are connected to the output of the regulator. Reg to Vin of Micro Board and, Reg to + of solenoid (just to be on the safe side)

2) Using 4x or 6x AA Alkaline (most available and cheapest around here) through the boost to board and solenoid in the same configuration as above.

3) An amended version of either of the above.

I have seen a lot of controversy regarding which method of external power is best and it is not my intention to instigate an argument. Any help will be greatly appreciated.

Thanks guys.

DrDiettrich

You'll find friends of whatever solution you suppose. Each one will give you different advice, the decision is up to you.

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