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Voltage sensor

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Gordon Tarling08/12/2018 12:55:23
235 forum posts
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I'm using a Q-X7S transmitter and a X4R receiver for a model boat. I'd like to get telemetry for the drive battery voltage (12V SLA) - any idea which sensor will work?

Thanks!

Edited By Gordon Tarling on 08/12/2018 13:16:08

CARPERFECT08/12/2018 14:25:56
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Give t9 hobbysport a call on 03456809549 they are the uk frsky main people, plus what is a 12v sla ?

They have two showing on their web site, but both are for lipo batteries

Shaun Walsh08/12/2018 14:46:00
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I presume SLA means sealed lead acid battery.
Andy4808/12/2018 14:47:14
1414 forum posts
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The simplest, and smallest, voltage sensor for the X4R is the FrSky FBVS-01. For some reason, T9 have never sold this. It is about £3 from BangGood.

**LINK**

Also the instructions for fitting it can be found in this documentation. Go to Section 10 part 2, the second "How To" section.

**LINK**

You will need a soldering iron. OpenTX can be adjusted to give the correct reading for a SLA battery.

Bob Cotsford08/12/2018 14:51:53
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You could use a resistor dividor to bring the voltage under 3.3v and use the a2 analogue input on the x4r or use an FBVS-01 sensor as here

Andy got there first!  The FBVS-01 appears to be a device with a selection of three dividor ranges.  I know GiantCod used to selll these, might be worth checking RCLife.

Edited By Bob Cotsford on 08/12/2018 14:55:03

PatMc08/12/2018 15:38:41
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4295 forum posts
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I bought these FBVS-01 sensors from RCLife. Used with D series Rx's for a couple for pre lipo ESCs on with 3s lipos. One thing to watch is that you only connect to the ESC +ve wire. Don't connect the -ve iwire as it's provided via the Rx A2 plug socket.

Gordon Tarling08/12/2018 16:07:30
235 forum posts
4 photos

Thanks for the advice chaps. I bought an FBVS-01 a couple of weeks ago and connected it up as shown in the documentation, but the Tx doesn't find it as a telemetry sensor. I did read that it will only work with the D8 receivers, which aren't compatible with my Tx, though that doesn't seem to be entirely true.

I'm wondering if the FCS-40A current sensor also gives battery voltage - does anyone know?

Bob - the resistor divider sounds feasible to me - will investigate that method.

Yes, SLA means Sealed Lead Acid battery - not much use in aircraft, but frequently used in boats.

I'll have another crack at the FBVS sensor tomorrow.

CARPERFECT08/12/2018 17:39:13
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499 forum posts
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You can re flash the tx , and have the option to get the tx to see D receivers. My friend did mine, so i can use my Delta 8 receivers.

Andy4808/12/2018 18:03:07
1414 forum posts
5 photos

CARPERFECT, reflashing the Tx is completely unnecessary, the OP is using an X4R receiver which works perfectly well with the FBVS-01 as shown in the documentation I linked to.

Gordon, basically the FBVS-01 is a simple resistor divider. The documentation I supplied the link to above shows how to wire it up to your X4R.

Gordon Tarling08/12/2018 18:08:42
235 forum posts
4 photos

Carperfect - I don't really want to be re-flashing the Tx if it can be avoided.

Andy48 - I'm fairly sure that I had the FBVS connected as shown in that documentation. However, I'll re-check the connections tomorrow and do some voltage/continuity checks if I can't get it working. BTW - very useful link to that documentation, I've not seen that before - thanks.

CARPERFECT08/12/2018 22:25:04
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499 forum posts
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I was refurring to Gordans coments regarding his Tx not being compatible with D8 receivers

onetenor09/12/2018 04:37:06
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1901 forum posts

You may get better /more accurate info on Model boats Mayhem or Model Boats Website. The latter especially

Bob Cotsford09/12/2018 10:31:08
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8149 forum posts
449 photos

The current sensors do indeed give the total battery voltage. My X4R sensors include a line VFAS in the telemetry section with the 40A sensor hooked up.

Chris Bott - Moderator09/12/2018 15:09:24
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I think Bob gives the best advice here.
Voltage A2 is a connection available on the side connector of the X4R. It's likely that the TX doesn't discover this until a voltage other than zero is detected on it.
Your 12v would require 2 resistors to divide it by 4 (so that A2 never sees more than 3.3v)

Then you'd have to set the multiplier in the TX to suit.
Andy4809/12/2018 15:26:17
1414 forum posts
5 photos

Many thanks for the disparaging comments Chris, and Onetenor!

I explored the FBVS-01 thoroughly before writing my documentation for OpenTX, and I now have at least 4 X4Rs running with FBVS-01 in them. It is perfectly suitable for the OPs use in a boat using a SLA battery. Essentially it is a simple resistor divider, and as the OP has one it makes sense for him to use it, rather than have to go about getting hold of the correct value resistors.

As so often the FrSky documentation is less than perfect and is not written the X4R receiver. I had to play around with the wiring for quite some time to get it to work correctly. I suspect if the OP follows my documentation, and discovers sensors again, it will work with no problem.

Sadly it seems pointless having spent months and months exploring, testing and writing 250+ pages of documentation when it is rubbished by a few who have never really followed it through.

Chris Bott - Moderator09/12/2018 16:08:41
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Woah Andy48 there's absolutely no need for that type of response.

I didn't know that the FBVS-01 was simply a resistor divider.

What we're doing then, is giving very similar advice. There are many more (polite) ways to point out the little gap in my kowledge.

I've learned something, I'm sure Gordon has.

Now with my moderator hat on - I'd like to keep this place as the freindly forum.
Gordon Tarling09/12/2018 17:07:25
235 forum posts
4 photos

Thanks chaps, got it all working properly this afternoon, using the FBVS sensor. Not sure what I was doing wrong previously though. I think I've calibrated it correctly, as it's showing the correct voltage on the Tx screen, so now I have to set up a low voltage alarm for it.

One thing puzzling me is that I keep getting 'telemetry lost' warnings during the setting up process - is this just because the Tx is very close to the Rx?

BobCotsford - thanks for that info, handy to know.

Chris Bott - Moderator09/12/2018 17:57:45
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That's good news Gordon. Clearly the best way to do it if you already have that unit. I might look out for some of those.

Yes, telemetry lost is quite common if the TX is too close to the Rx. I wouldn't worry about that.
Bob Cotsford09/12/2018 18:31:14
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8149 forum posts
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Chris, these were the original D series voltage sensors that have fallen out of favour as most people just use the LiPo sensor for external voltages these days. I must admit that I never bought one myself preferring to use a high value screw adjustment miniature pot to act as a divider when I used to only worry about the total pack voltage. We're a bit spoiled with X series SPort sensors now.

Gordon Tarling10/12/2018 17:54:33
235 forum posts
4 photos

Chris, the FBVS sensors are readily found on 'the bay'.

Bob - will bear in mind that a small pot will work just as well. I'm guessing a 10k pot would be OK?

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