AX1500SC Unresponsive To Pot Input

Thanks in advance for any help you can provide.

Controller ID: RoboteQ AX1500-SC
Software Rev. v1.9g 11/02/09
Hardware Code: 1-3-1

Controller Configuration Utility: v1.9f 08/14/09


We have what is likely a minor issue with our AX1500-SC controller in that it does not seem to respond to the potentiometer input on channel 1 at pin 11(nor channel 2 at pin 10 - which, of course, should be normal for the SC).

As we manipulate our pot and watch channel 1 (Ana 1) in the RUN tab of the Roborun utility we can see our input value ramp from 0 to both 127 and -127 so it seems as though the controller is in fact receiving the input.

The controller seems to respond perfectly when commanded from the Roborun Utility and drives our motor as expected. Upon finishing with Roborun we reset the Controller Input to Analog in the Controls tab, disconnect the RS232 connection and reset the controller.

In our application there are no potentiometers connected to the controller when it is first powered and so we have unchecked the Enable Center at Startup Safety option in the R/C -Ana Specific tab of the Roborun utility.

We have tried powering the controller while the pot was attached and centered and had no better luck and so think this isn\'t the issue but, of course, at this stage we don\'t know anything for sure.

The jumper setting for single channel operation appears to be in the correct location (as set from factory).

We\'d noticed in other threads the advice given to reinstall the Roborun Utility and we have done so. We\'ve also reinstalled the Main Firmware for the controller using file axfirmware19g-110209.zip from the RoboteQ website.

The manual speaks of some 47k resistors used to maintain 2.5v at both the channel 1 and 2 inputs in the event that no joystick or pot is attached. Are these resistors built into the board and if so, are we fine to start the controller with no pots attached even if the Enable Center at Startup safety is left \"on\"?



Is there something we\'re overlooking here?

The only explanation that comes to mind is that the controller does not see the pot as being centered after reset.

Check with roborun that you see the analog input value at 0 when the pot is centered or disconnected.

It is also possible that the firmware looks also at channel 2 input even though it is not used in the single channel configuration.

Pls double check and report if problem is confirmed.

Thank you Cosma for the quick reply!

We put a couple dummy resistors in place to mimic a centered joystick for both channel 1 and 2 inputs and the controller seems happy with it. The controller now follows the input of our potentiometer.

Does this mean the Enable Center at Startup Safety check-box doesn\'t do anything? I\'m not familiar with hyper-terminal commands but is there a command structure that we can use to disable the startup safety?

It may be that there is a problem with the disabling. We will investigate and post next week.

Hi Cosma,

Just wondering if you have any new info on this. We still seem to have an issue where we cannot disable the Center At Startup Safety feature with the Roborun utility.

While playing with our controller today I noticed that if it is powered while connected to the comm port of our PC, and not connected to the Roborun utility, it will respond to an analog input at pin 11 (channel 1). The connection to the PC can even be removed and the controller continues to respond properly until power to the controller is reset (while not connected to the comm port of the PC).

Previously, I thought we had an issue with the Center At Startup Safety feature, now I\'m not so sure. Is this a glitch you have some experience with or is it still possible this is related to the Center feature?

When connecting the RS232 cable, you are floating the Analog inputs, so they will be centered to 2.5V because of the internal pull up and pull down resistors.

You should be able to set the disable bit with the console.

Read the current value of parameter 5 by sending \"^05\"

Look at the reported value and set the lowest bit (if 00, make 01). Then save that value to the controller by sending \"^05 01\" (replace 01 by the new value). Restart the controller.

Thank you again for your response.


I followed your instructions and it does appear to toggle the Center Safety feature on and off, as evidenced by the check mark either showing up or disappearing from the R/C-Ana Tab in the Roborun utility. Unfortunately, this didn\'t change the behavior of our controller.

One thing I didn\'t make clear previously is that we wired a remote RS232 port off the 15 pin connector of the AX1500SC board. This allows us to maintain a connection to our input pot while connecting to, or disconnecting from, a PC.

The strange behavior we\'ve noticed is that the controller will not respond to our pot if the controller is powered up while disconnected from the RS232.

If, however, we power the controller with an RS232 connection between the board (via our remote access port) and our PC, the controller responds to the pot perfectly (remember that our pot is simultaneously attached to the controller). The Roborun utility DOES NOT HAVE TO BE RUNNING, the simple fact of having the controller connected to the comm1 port of a PC is enough to persuade the AX1500SC to respond to the input pot.

Once the controller has been powered up in this fashion we can disconnect the RS232 cord and the board will continue to respond to the pot and we can use it normally.

We\'re at a loss as to why the controller is behaving like this.

We\'ve tried reflashing the controller firmware using the file available on this site twice. We\'ve un-installed and re-installed the Roborun application on our PC.


Do you have any suggestions as to how we might solve this odd little problem?

Make sure that the pot takes the power from pin 14 (5V) and pin 5 or 13 for GND.

Our serial cable does internally jumper pin 14 and pin 7 and pin 13 and 6.

If you power the pot from pin 7 and/or 6, it will see power only when our cable is plugged in.

Other than that, there is no known reason why the pot would not always work.

There is a potential pitfall with the feedback pot connection when in closed loop mode. But if you are running in open loop, pot 1 is always active.

As far as firmware and hardware go, if you can see the ana values change on Roborun in the run screen, then your pot is wired ok and the controlers sees it.

There\'s a new twist to the saga but just to respond to some of your previous points first, our pot is powered from pin 14 and 13 for GND, we are running in open loop mode and we can see the analogue values change in the Roborun Utility when we swipe our pot.

What we\'ve recently discovered is this, if we tie pin 2 of the DB15 connector to ground through a 150 ohm resistor the controller powers up and responds properly to the pot input. Have you seen this before or can you shed any light on why this would seem to remedy our problem? Additionally, is there the potential for harm to the controller in this scenario?

Naturally we\'d remove this resistor in the event we wished to connect to a PC and use Roborun (we have the resistor set up on a plug).

Thanks again for any info you can provide.