openinverter forum

Hi Johannes

May i ask if the design of the voltage sense circuit can be changed to output 0 to 5V function?
It could then be used in other applications as well.

If i would then use 680K / 470R divider on HV side how do i change the op amp side to get up to 5V out (up to 4.7V really)?
Do i just replace the 1K2 resistor to change gain? Do i increase it or decrease it? I see opamp is reverse type...

tnx

Arber

Of course i went and changed the circuit like i said.

I changed R8 (op amp gain) to 4K7 value and I removed one 680K resistor on HV side. I kept only R2.
When i increased battery past 380Vdc i would get 3.38V and no more. If i increased voltage further indication would jump to 1.9V and remain there. I see this as comparator issue. So i added one 100K resistor in place of R3 and true enough i could now increase the voltage past 400Vdc.

In the end i changed two things:
1. R8 value is changed to 4K7.
2. R2 value is changed to 100K.

Now i can reliably get 0.2V to 3.4V voltage reading for HV value from some 60V up to 400Vdc.

Hi Arber333

On the subject of Voltage sense boards. I wish to calibrate voltage on my Rev2 and was wondering about the connector X1. Is this just for calibration or is it an absolute requirement and a permanent connection for UDC. ? Am I missing something here as it does not seem right. Hope I am not being silly !

Regards
Stephen

Hi Stephen,
I'll just jump in for Arber here.
X1 is how the inverter monitors battery voltage. It is necessary for precharge, overdischarge protection, overvoltage prevention, and changing of parameters as battery voltage changes.
So you do need it permanently connected, unless you have a different voltage monitor (maybe a CAN bus monitor? That would be cool ).

-Isaac

Ok, my rambling was about the voltage sense circuit at general. Not used in open inverter. I just borrowed Johannes idea and use it for precharge sensing and voltage control in my Lebowski board.

That said, yes this connection is vital to precharge and voltage sensing of inverter.

Thanks Guys.

So, I actually do connect a e.g. 360V or whatever my DClink connection is to X1 ?

Regards
Stephen

Stephen Darbey wrote: ↑Sun May 03, 2020 11:24 pm So, I actually do connect a e.g. 360V or whatever my DClink connection is to X1 ?

Precisely. Might want to add a fuse if you have to make a long run or there's danger of a short.

-Isaac

Thanks Isaac, Arber.

That's cleared that, 'looks right' doubt up. (What if moment ?).

Regards
Stephen

Complete newb here reading through posts. Just installed my dual motor board in 2012 gen 3 prius inverter. Does the dual motor board already have voltage sense on board? And is battery voltage available through can from the dual motor board?

If not is there a voltage sense board available that could also be used with a shunt so i can get battery volts and amps on my lcd dash.

slociviccoupe wrote: ↑Fri May 13, 2022 12:13 am Complete newb here reading through posts. Just installed my dual motor board in 2012 gen 3 prius inverter. Does the dual motor board already have voltage sense on board? And is battery voltage available through can from the dual motor board?

If not is there a voltage sense board available that could also be used with a shunt so i can get battery volts and amps on my lcd dash.

There was, EV Display, but not anymore and it was not open source.
I think majority of us now use ISA shunt with CAN bus reporting.
You could setup inverter to output inverter voltage as CAN data stream. But then that wouldnt work with charging when inverter is not active.
Now i only use BMS as a shield and i take chargers own HV CAN report to control charging and i use EV Display for direct voltage reference to driver.
I am working on using ISA shunt with 2.4" OLED display that would be connected to CAN bus. OLED has much better resistance to UV and temperature than common LCDs.