Settings appear to change when USB Disconnected

Questions about using encoders with the Roboclaw product line
bearbait
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Joined: Thu Oct 19, 2017 11:41 pm

Settings appear to change when USB Disconnected

Postby bearbait » Wed Feb 07, 2018 10:25 am

I am using latest software version (4.1.24) Roboclaw solo with analogue potentiometers for control and feedback with a linear actuator. I can get close to linear operation from 0 - 100% using IonStudio (1.0.0.56) but when USB is disconnected errors appear e.g. at 0% extension with USB it goes to 5% extension without any change of potentiometer control. I have checked that the control voltage is not changing.
What is causing this?
Kind regards
Bearbait

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Basicmicro Support
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Re: Settings appear to change when USB Disconnected

Postby Basicmicro Support » Fri Feb 09, 2018 10:19 am

Please describe how you have the linear acuator feedback wired to the Roboclaw? I assume it is an integrated linear potentiometer in the actuator? What is the pots resistance(from gnd to pwm wires)? How is it connected to the Roboclaw(did you use the recommended resistor in series with the pwm wire as described in the manual)? What is the voltage range on the signal pin of the linear pot when the actuator is fully closed and opened?

Sorry about the delay getting back to you. I was at a trade show all week and just got back. It was not possible to answer posts while I was gone.

bearbait
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Re: Settings appear to change when USB Disconnected

Postby bearbait » Sat Feb 10, 2018 9:16 am

No problem with slight delay.

Yes, the feedback is an integrated linear 10 turn 10k potentiometer. Because the actuator extension is deliberately by design restricted to 38% of maximum, the feedback potentiometer range is 0 to 3.8kohms.
The actuator is a Gimson Robotics GLA80000.
The control potentiometer is also 10k linear.
0 volt reference for both pots is wired to solo pin 1 (gnd)
control slider is wired to solo pin 3 (S1)
feedback slider is wired to solo pin 10 (1B)
The feedback potentiometer supply is 4.096 volts derived from the solo +5v using a TI precision shunt regulator.
The control potentiometer supply is 2.048 volts derived from the solo +5v using a TI precision shunt regulator.
In this way the feedback range/resolution is maximised at 38% of 4.096v = 1.556v (theoretical)
With no USB connected to the solo, the resistance from either potentiometer 0v connection to the solo battery negative connection is less than 1 ohm (either polarity) when corrected for lead resistance.
The actual measured voltage range is:
0v control = 0v feedback actuator open
2v control = 1.483v feedback actuator closed (it looks like the solo input pin is loading the circuit slightly)
There is no resistor in series with the pots as regulators drop voltage, see above.
I do not understand "resistor in series with the pwm wire as described in the manual" - do you mean from 5v to pot? - Not needed, see above.
With USB connected the actuator extension goes 0mm to 201mm as required by design.
Without USB connected it goes from 9mm to 201mm.
QPPS = 420 for both speed and position
Position P = 5000
I = no real effect, can be set to practically anything
D = no real effect, ditto

Note: Today I checked another solo from previous work in another (but similar) circuit, same usb lead, same software, same pc. It does not shift calibration when connected/disconnected.

Weird or what?
Kind regards
Bearbait

bearbait
Posts: 13
Joined: Thu Oct 19, 2017 11:41 pm

Re: Settings appear to change when USB Disconnected

Postby bearbait » Sat Feb 10, 2018 9:27 am

I would have attached a no USB calibration chart pdf format but you seem to have attachments disabled? All file extensions seem to be invalid.
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Bearbait

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Re: Settings appear to change when USB Disconnected

Postby Basicmicro Support » Sat Feb 10, 2018 12:02 pm

The I/O pins have a 100ohm resistor in series along with a 3.6v zenor diode. This is for current limiting and overvoltage protection on the I/Os. This is the extra loading you see on the feedback pin.

If only one unit is showing the problem I would have to guess a hardware problem. Short of sending it in though it would be just a guess as to the cause though obviously related to USB and probably VBus specifically. There are protection circuits on the VBus input of the Solo. We dont power anything from VBus but we do read it to detect the unit is plugged in.

With linear actuators I and D usually have little effect. Between the very slow speeds, the low resolutions on the encoders and the significant backlash usually present on these types of actuators I and D usually cant do anything to improve performance noticably.

Did you buy both Solos at the same time? If not, which is newer? You can send the oddly functioning one in and we will go over it to diagnose the cause of the problem.

bearbait
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Joined: Thu Oct 19, 2017 11:41 pm

Re: Settings appear to change when USB Disconnected

Postby bearbait » Mon Feb 12, 2018 3:51 am

Yes, both units were purchased at the same time late last year. One has been set up and tested for a a couple of months. The one with the problem had not been used until recently as we were waiting for the actuator to be delivered.
I am discussing with the purchaser about what to do next.
Kind regards
Bearbait

bearbait
Posts: 13
Joined: Thu Oct 19, 2017 11:41 pm

Re: Settings appear to change when USB Disconnected

Postby bearbait » Mon Feb 12, 2018 7:26 am

These Solo units were both purchased from your UK distributor, Active Robots. Should we return the "strange" unit to them for sending on to you or direct to you?
If direct, please advise shipping address and contact name.
Thanks again.
Kind regards
Bearbait

bearbait
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Joined: Thu Oct 19, 2017 11:41 pm

Re: Settings appear to change when USB Disconnected

Postby bearbait » Tue Feb 13, 2018 3:14 am

Your Forum web site is blocked by Avira anti-virus saying that there is an "HTML/fakealert virus pattern detected". The only way that I can get to the site is by using Linux with no AV active.
Kind regards
Bearbait

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Basicmicro Support
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Re: Settings appear to change when USB Disconnected

Postby Basicmicro Support » Tue Feb 13, 2018 9:16 am

You can send the unit directly to us. Please copy the return address from our Contact page on the main website.

Include your return address inside the package with your contact information. We will cover the shipping back to you.

P.S. I also use Avira and it detects no virus when I access the forums. If this happens on a specific post please let me know the link. I also suggest a secondary scan of your own computer just to be safe. Here is some more information on that warning: https://www.microsoft.com/en-us/wdsi/th ... /FakeAlert

bearbait
Posts: 13
Joined: Thu Oct 19, 2017 11:41 pm

Re: Settings appear to change when USB Disconnected

Postby bearbait » Thu Feb 22, 2018 3:04 am

Unit returned. Sent by TNT Monday 19th Feb.
Kind regards
Bearbait


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