RoboInterface: 2 motors using only 3 connections ?

[hvn]

Hi,

Using a RoboInterface, I'm trying to control 2 motors with just O1, O2 and O4 available. O1 and O2 are for red/green of 1 motor, which (of course) works. After connecting the 2nd motor (combining either green or red), despite programming it only works in 1 direction. Unless I reverse the connectors, of course. So the question is: is it even possible to fully control 2 motors with just O1, O2 and O4 using programming?

hvn

[steffalk]

Hi,

If you can accept a motor running slower, you could try a voltage divider. The outputs of the RoboInt are either 0V or +9V. If you connect two resistors (for example, fischertechnik light bulbs) serially between 0V and +9V, and attach one line of the motor to the middle (between the two resistors), it could possibly turn in one direction if you turn the RoboInt output off, and in the other direction if you turn it on. It could depend, however, on the kind of electronics used inside the RoboInt. Turning the motor off would be achieved by setting RoboPro to some mid-level output level, as near as possible to the voltage measured between the two resistors.

Success,
Stefan

[jona2004]

Hello hvn,
While I do not have a Robointerface I used another solution on the TX.
The solution described below allows you to drive n motors with n+1 outputs as long as not two motors must run at the same time.
Each motor can run both directions and can be speed controlled from 0 to maximum speed.
In your example the connection is as follows:
O1 connects to two motors as a common connection
O2 connects to M1
O4 connects to M2
In the table below symbol 'S' is speed so 1 ... 8 or 1 ..512. If there are two Ss in the same row the value must be the same

Code: Alles auswählen

       |  O1  |  O2  |  O4 |
       +------+------+-----+
       |  0   |  0   |  0  |  both off
       +------+------+-----+
       |  0   |  S   |  0  |  M1 right
       +------+------+-----+
       |  0   |  0   |  S  |  M2 right
       +------+------+-----+
       |  S   |  0   |  S  |  M1 left
       +------+------+-----+
       |  S   |  S   |  0  |  M2 left
       +------+------+-----+
       |  0   |  S   |  S  |  M1 right M2 left Attention O1 must sink 2x the current!
       +------+------+-----+
       |  S   |  0   |  0  |  M1 left M2 right Attention O1 must source 2x the current!
       +------+------+-----+
       | S    |  S   |  S  |  stop
       +------+------+-----+
 

Disclaimer - tried out onTX using only operands ("orange lines") assuming those get calculated in one round so the ouputs are updated at the same time and they did.
Good luck Joachim

[hamlet]

Hi Joachim,
Awesome! This is a great idea. Thanks for posting it.
Cheers,
Helmut

[hvn]

Hi,

Thank you for your answers. Unfortunately, the motors have to be able to operate at the same time. Otherwise, great ideas.

hvn

[ThomasW]

Hi

is it even possible to fully control 2 motors with just O1, O2 and O4 using programming?

It is not possible to do so.

Each motor has 3 states (off, left, right), thus 9 states in total (3 x 3).

With 3 outputs you have 8 different values (2 x 2 x 2), not enough for 9 states.

Regards
Thomas

[hvn]

Hi,

Thank you for pointing this out. This means that I will have to use a RoboIOExtention if I want to continue...

hvn