0
\$\begingroup\$

I am aware the arduino requires at least 250mA and to power several components 1 amp would be better. source [http://playground.arduino.cc/Learning/WhatAdapter]

This is a motor the driver I am using and upon scrolling down it said 2 amps is the driver IO and driver supply should be anything from 5v to 46v.

I am powering my robot using a 9v source along with 2 resistors, one 4.7 ohms and the other 10 ohms. The resistors and power supply are in the center. My question is will this setup work without heating and/or blowing up (Im just a bit paranoid).

\$\endgroup\$
  • \$\begingroup\$ Forget the resistors. The parts will draw whatever current they need. I would recommend a 12V SLA battery though. 9V batteries may not be able to handle the current draw very well. \$\endgroup\$ – DerStrom8 Aug 22 '16 at 16:13
2
\$\begingroup\$
  1. The current you have marked for the motor is only correct if there is a short circuit instead of the motor. That resistor will reduce the current and the voltage to the motor.
  2. If there were 1.9A through the 4.7Ohm resistor, that would be 9V*1.9A=17Watts of power. What resistor were you going to use for that?
  3. Questions (1) and (2) also apply to that 10Ohm resistor you have feeding the Arduino. You will have losses, the Arduino might not run, and that resistor will get hot and/or need to be made for higher power than the typical 1/4 Watt resistors you will have at hand.
  4. Don't power your servo off the regulated 5V from the Arduino. The servo can draw a lot of current and cause the Arduino processor to reboot or hang. The garbage from the servo could (potentially) kill the processor.
  5. Please tell me you aren't planning to use a 9Volt battery. They don't last long when driving motors. They also don't like to provide much current. They are made for small current (like, less than 100mA) tasks like running a transistor radio.

Fixes:

  1. Ditch the 10 and 4.7 Ohm resistors.
  2. Power the servo from the 9Volts, or through a separate regulator. DO NOT use the regulated 5V from the Arduino.
  3. Either use a 9V powersupply, or a different battery to power your motors and the servo.
\$\endgroup\$
  • \$\begingroup\$ I am using 6 AA rechargeable batteries together to form 9 volts \$\endgroup\$ – Don Grey Aug 22 '16 at 17:17
  • \$\begingroup\$ Also what if I leave the servo to the 5v and connect a decoupling capacitor to it \$\endgroup\$ – Don Grey Aug 22 '16 at 17:22
0
\$\begingroup\$

When driving inductive loads with a DC resistance or DCR, there is a motor surge current on starting equal to the V/DCR. In efficient motors this can be as much as 8x the rated load current running at full speed.

It is wise to use separate supplies that give much lower ESR impedance along with the Bridge driver RdsOn than the DCR of the motor such that voltage sag is limited to some practical value such as 10% max.

THe reason we do this is to minimize the I^2R losses in the current loop and then considering total load power choose a % loss from the battery and switches to reduce self-heating.

Thus you need to determine the DCR of the motor and then choose a bridge driver RdsOn and choose a power supply that can deliver the peak current with x% voltage drop.

If you do a load test on your AA batteries you can expect a fairly high ESR in the 1 Ohm Range, while LiPo batteries are much lower and may be better suited to this.

You also need to consider the Amp-hour and C discharge rating of the battery under load to retain achieve the potential life charge cycle of the battery. These may be 1C, or C/10 for example.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.