Where to connect RS422 termination resistor's

I'm not familiar with your data logger so I can't give a specific answer. However if you think the issue is caused by the lack of termination then I'd first try shorting the connection length between the devices and or lowering the data rate. If you have a short cable it will reduce any reflections and if you use a low data rate any reflections will have died down before the data has been sampled. So if the problem exists with a short cable it's probably not a signal integrity issue,  Here is a good white paper on  RS422/485 which has a section on termination http://www.bb-elec.com/Learning-Center/All-White-Papers/Serial/RS-422-and-RS-485-Applications-eBook/RS-422-RS-485-eBook-graphics-embedded.pdf

Hello Colin,

Thanks for the reply and the information, will have a good read.

The Ever Solar, Solar Eye wireless unit is connected to the inverters RS422/485 interface board via a short 500mm RJ45 cable and the interface card has two ports to allow daisy chaining of other Inverters or devices.

The problem with the Solar Eye wireless data logger unit is that it works most of the time, but for some reason there are days it will not work at all and powering the inverter off then on does not fix the problem, I have contacted the manufacturer but they no longer manufacture the unit or support it any longer, it could be a firmware problem with the wireless unit as my Brother-in law has the same Inverter and Solar Eye and he has the same problem.

If it is a firmware problem I can live with it, but if it is something like an unterminated unused RS422/485 port "see attached JPG image" then do you think adding termination resistor's to the unused port with an RJ45 connector would eliminate any reflections or noise if there are any?

Regards Andrew

ndrew

I don't suppose you have noticed any similar environmental conditions on the days it doesn't work? Like hot or really humid days?

Hello Michael,

This problem with the wireless unit not working intermittently appears to happen during the colder month's, as I stated, I can turn the inverter off then on and this makes no difference and when I try the rebinding procedure for the receiver unit it will not bind to the transmitter. Worst case the unit didn't work for three straight days, it did not matter how many times I turned the Inverter off and on or repeating the rebinding procedure, it would not work, I even swapped the RS422/485 interface board with a spare they provided with the Solar Eye kit, made no difference.  

Then miraculously, it would then work fine for a few more weeks or month's, so it it is either a firmware problem with the transmitter unit or maybe it requires some sort of bus terminator on the unused port?

I sort of suspect it may be a design or firmware problem since the manufacturer no longer manufacture the unit, probably because of the problems I described and then put it in the too hard basket, but they still have a hardwired unit Power Monitoring Unit

Regards Andrew

From what I'm reading, the wireless portion of the unit won't even work. I'm having difficulty believing it could be the cable termination that interferes with the wireless. Are they connected somehow?

Yes that is correct, I can turn the Inverter off then on, repeat the binding procedure and no go, then leave it, and the next day it will be working fine, as you can see the RJ45 cable is short so you would not expect any terminating resistor would be required.

This web site for the ever solar data monitor https://code.google.com/p/eversolar-monitor/wiki/Hardware shows optional termination but for cable runs over 10m's.

the Ever Solar RS422/485 interface card

I think I'd have to look at it. But as another obvious thought, have you tried replacing the cable?

Guys

Having a look from this side, there seems to be some discussions here.

http://www.sjcnet.id.au/computers/eversolar-inverter-monitoring-with-linux

code and some info

https://code.google.com/p/eversolar-monitor/

It seems that they are still available in Australia up until 2012.

You haven't mentioned what is on the end of the cable and how it connects with your PC/RPi.

Maybe this helps.

Mark

To Micheal, no I have not swapped the cable, but I can try, might take a while for results.

To Mark, I am aware of those sites, the system I have is manufactured by the Manufacturer of the Inverter, Eversolar, now named Zeversolar who are now owned by the SMA company.

The wireless setup consists of the transmitter unit which is in the above images called Solar Bee and a wireless receiver unit called the Solar Eye which displays Inverter information on an LCD display and stores Inverter power data onto an SD card for viewing on a PC in CSV format.