RC project

Using Arduino Motors, Mechanics, Power and CNC
1

So i have a motor which will go forward when positive and negative are connected, and backward if they are reversed..
Arduino can not handle the current draw for the motors, so i'm only using the arduino to trip a relay. two actually

I'm using a 7.2v battery, and using a single state (i think this is correct) relay

looks like

C
-------------/ ----
C

So i have it working in a single direction, but i cant figure out how to wire it for forward and reverse, when i do the single relay, for forward, works great.
When i attempt to throw the reverse current, soon as i connect power it somehow finds a loop i missed and just goes without the relay triggered...
definitely a wiring problem and i've tried to think it out logically, but just doesnt seem to work.

So end goal i'd like to see is 2 relays, external power, and arduino to make two loops of current, power one way, then power the other.
Have transistors on hand but dont really know how to use them yet...

2

Think you need to check an H bridge, see e.g. - http://itp.nyu.edu/physcomp/Labs/DCMotorControl - read with care

There are different chips for different loads ...

3

Hi, try:

  • You have two "form C" relays, one moveable common connection, one normally closed, one normally open??

  • Connect motor to the two moveable "com" terminals.

  • Connect both Normally open terminals to +

  • Connect both Normally Closed terminals to - GND.

Motor does not turn with relays off. One relay causes rotation one way, other relay causes rotation the other way.

BTW: Both relays activated? Motor also stops...

Let us know...

4

I'm using relay with a single com, N/O and N/C is the same

as picture above shows, it doesnt have a normal open, and a normal closed, it's just the single, it's open when not active, and closed when active.

So for example,

Pin 13 Arduino, connects to coil, and ground to coil.
7.2 V battery on top and motor positive to bottom of relay. When active 7.2V gets applied to positive for motor, and ground is direct connect from motor to battery. This functions fine.

Now what i'm trying to do is with another relay, the exact opposite, i need motor positive, to ground, and the battery positive to motor ground. so this is where i'm having flaws.

5

Tried posting a picture, they just arnt coming out to clear, so going to try to explain with kinda diagram

+7.2 ---relay -- Motor +
-7.2 -- Motor -
Activate relay, motor goes forward.

+7.2 --- relay -- Motor-
-7.2 -- Motor +
Activate relay, motor goes backwards.

Now getting both to function is causing me headaches.
+7.2 --- breadboard, take two leads from BB to two relays, so now we have
+7.2 -- relay-- Motor +
+7.2 -- relay -- Motor -
-7.2 direct to motor -
This causes motor to go forward but not backwards, due to Motor + isnt grounded.
If i ground the motor+
-7.2 direct to motor+ the motor goes forward without activating either of the relays, because somehow it gets a + to + and - to - connection.
this is where my wiring is horrible :slight_smile: really just a wiring problem.

6

I'm using relay with a single com, N/O and N/C is the same

Oh. You have only "form A" normally open relays.

You will need 4 of those relays to run the motor both ways.

  • 2 relays: common to a motor terminal, Open contacts: 1 to + 1 to -
  • SAME for other motor terminal.
    BUT now you have to be very careful not to energize 2 relays on same side at once, connecting + and - directly!! Better put delays in before each switching direction...