by DaveTheRave » 05 Jul 2016, 09:28
Hi guys, I’m new to the world of power chairs. Very grateful to this forum, it has helped me get this far quickly. Please forgive me for a long first post, in which I tried to put pctures but failed.
A work colleague has a Quickie powered chair with a VR2 JSM controller (D51269.01). All is fine, but we are located some way from the nearest repair centre and having him out of action due to a fault on the chair is not acceptable. A second chair was bought second hand as a spare, the chairs match but the second has a VR2 JSM-A-L controller (D51269.02). This has been ‘adjusted’ and the driving control is not right. Somewhere the settings are off and cause some unexpected reversals of direction.
Your forum was found and an attempt at building a usb to serial lead made, but this failed. At this point I was called upon to get things working.
I took the lead we had, read up many pages from this site, and tried connecting. Comms inactive. Then got out some test kit. An oscilloscope showed up a problem
(Scope36b)
This trace shows the signal going to the chair, followed by the chair’s response. Sadly the reply is too small for the RX circuit to consider it a proper signal, so it is ignored. I tried quite a few options to fix this, but nothing worked. So as it was 5 o’clock I went home to think about it.
Next morning I arrived with great plans to throw some serious electronics at the communication problem, but over the first coffee of the day I read some more pages from the forum. I found this picture posted by DSmidget
(Programmer cable)
This is my kind of information, it tells me stories and makes life so much simpler. So I got building and in a couple of hours and a couple of tries had this,
(interface)
It uses the biasing/matching circuit from the interface pictured above, and amplifies the return signal to give the RX circuit a chance. The joy when the programming software went over to comms active and then read the settings from the chair; this caused an outbreak of happy dance. The circuit may be robust enough to work with almost any USB to serial convertor that has a 5v line. However I have only tested with 2 types here and they both work, one is a FDTI and the other a cheap 3 wire device which I had to break open to get at the 5v. Neither worked with just a diode, or with the addition of a pull up resistor.
I copied the settings file from the chair that works well and, after saving a copy of the poor settings, loaded it into the second chair. Brilliant, the second chair now drives just like the first. But we have lost the use of the actuators that control the seat tilt. Humphf.
So as we only have the service version of software, we cannot adjust parameters on the chairs to get the second controller to drive nicely and control the seat tilt. I have printed out the settings from both chairs and can see where the setups differ, it would be great to be able to get full function of the second controller.
Anyone care to drop me the full software?
- Attachments
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- Signals sent and returned on RX and TX lines with normal usb cable
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- courtesy of DSmidget
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- Biased and amplified interface