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### Topic: Help with the circuit (Read 1 time)previous topic - next topic

#### TomGeorge

#15
##### Feb 17, 2018, 02:47 pmLast Edit: Feb 17, 2018, 02:48 pm by TomGeorge
Hi,
Where on a Pro Mini is the 3.3V?

Tom...
Everything runs on smoke, let the smoke out, it stops running....

#### hardik311095

#16
##### Feb 17, 2018, 02:50 pm
Don't power the motors through the tiny (<150mA) regulator of the ProMini.
Connect motor(+) directly to batt(+).

Connect them directly to batt(-), not via ProMini ground pins.

Are extra resistor needed to protect the motor from direct connection from battery?

Where to place them in the circuit? Assuming I calculate their values according to the voltage drop of the battery and the current supplied.

#### TomGeorge

#17
##### Feb 17, 2018, 02:52 pm
Hi,
I know you can get 3.3V Pro Mini, but the link the OP provided made no mention of 3.3V

Tom..
Everything runs on smoke, let the smoke out, it stops running....

#### wvmarle

#18
##### Feb 17, 2018, 02:53 pm
So... 70 x 6 mA for the motors, plus 50 mA for the Arduino (probably less as it's a Mini so pretty barebones) makes 470 mA.

So battery size needed is 470 mA x 4 hours / 0.7 (effective charge) = 2,700 mAh.
That's a high capacity 18650 battery, or a battery like this one from Adafruit.

I know you can get 3.3V Pro Mini, but the link the OP provided made no mention of 3.3V
OP mentioned it's a 3.3V version in #0.
Quality of answers is related to the quality of questions. Good questions will get good answers. Useless answers are a sign of a poor question.

#### wvmarle

#19
##### Feb 17, 2018, 02:55 pmLast Edit: Feb 17, 2018, 02:56 pm by wvmarle
Are extra resistor needed to protect the motor from direct connection from battery?
No.

Basic wiring is battery pos - motor - transistor - battery neg.

Furthermore: you won't blow up those motors with a little extra voltage. You're going to regulate them anyway (PWM), so they get pulsed, and that way the effective current is brought down to whatever you need it to be to get them up to the speed you want to go.
Quality of answers is related to the quality of questions. Good questions will get good answers. Useless answers are a sign of a poor question.

#### hardik311095

#20
##### Feb 17, 2018, 03:00 pm
Thanks Guys, I finally have a direction to proceed. You guys are awesome.

#### CrossRoads

#21
##### Feb 17, 2018, 04:13 pm
ProMini's regulator is only good for 150mA.
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.

#### hardik311095

#22
##### Feb 18, 2018, 09:40 am
Don't power the motors through the tiny (<150mA) regulator of the ProMini.
Connect motor(+) directly to batt(+).
Same for the emitters of the 2N2222 transistors.
Connect them directly to batt(-), not via ProMini ground pins.

For full saturation of the 2N2222 transistors (max motor power), base current should be 10% of collector current.
Lower the 1k resistors to 330ohm.
10n across the motors is more than enough.
Try to avoid pin13. That pin could change state during bootup.
Leo..
I have uploaded the new circuit. Is it okay?
Do I need to connect something to the GND. Any other problems that you see?

#### TomGeorge

#23
##### Feb 18, 2018, 10:12 am
Hi,
Where is the new circuit?

Tom...
Everything runs on smoke, let the smoke out, it stops running....

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