XR8 rx telemetary sensors

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aadamson
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Re: XR8 rx telemetary sensors

Post by aadamson » Wed Oct 23, 2013 3:58 pm

Thanks for the quick sanity check. Let's roll with what we have or we'll get into to much creeping elegance. :) I'll add the .1 on the vd side any other changes you can think of?


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MikeB
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Re: XR8 rx telemetary sensors

Post by MikeB » Wed Oct 23, 2013 4:03 pm

None that I can think of, just this 0.1 across R3.

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Re: XR8 rx telemetary sensors

Post by aadamson » Wed Oct 23, 2013 4:41 pm

MikeB wrote:None that I can think of, just this 0.1 across R3.

Mike.
And that's a bypass cap to ground correct?

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Re: XR8 rx telemetary sensors

Post by MikeB » Wed Oct 23, 2013 4:43 pm

Yes!

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Re: XR8 rx telemetary sensors

Post by aadamson » Wed Oct 23, 2013 7:11 pm

MikeB wrote:Yes!

Mike.
Ok, all done... design updated for the bypass cap on the AIN side, and I changed the 3 pin connector on the AIN side to a 2 pin, no sense in having 3 and nothing connected to the center pin when it's primary design is to sense voltage +/- :)

latest version in eagle here...
https://github.com/akadamson/X8R-Analog-Sensor

I'll add a zip file with the OSHPARK gerbers and I'll share out the OSHPARK file once I submit it so other can just order as they like...

My basic plan is as follows.

I'm going to order 3 boards and at the same time submit this brd file to have it panelized into a 2x5 panel array. I'll most likely submit that as well and I'll need to get 3 of those boards for 30 total. They will send me back the paste layer so that I can get a stencil done for the 2x5 layout... the 3 individual boards I'll build as test boards.

Mike, how can I send you a couple the simplest and easiest way? *no need to reply to that here, drop me a PM*.... And it's going to be a week or so before I see boards anyway...

Updated BOM here - http://www.sandsquid.com/#yWS4Ms

I guess we are off the races as they say... Maybe this will be incentive for frsky to get their boards out quicker :)..

Alan


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MikeB
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Re: XR8 rx telemetary sensors

Post by MikeB » Wed Oct 23, 2013 7:59 pm

Bother, I'm still using Eagle 4.16 so I can't view your files.
I can't, therefore, see what you've done regarding the 3 to 2 pin connector. I used a 3-pin one, with the middle pin removed, to match the analog input connector of the 'D' series receivers. The idea was to make it easy for those that wanted to upgrade to a X8R, and already had something plugged in.
Thinking about it, as long as a 3-way socket will mechanically fit, they would just need to move one of the socket inserts over one place in the housing.

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Re: XR8 rx telemetary sensors

Post by aadamson » Wed Oct 23, 2013 8:22 pm

hang on, I'll post a screen shot...

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Re: XR8 rx telemetary sensors

Post by aadamson » Wed Oct 23, 2013 8:24 pm

I can just as easy go back to the 3 pin, it's just a swap of components... I've not ordered the panel boards yet, just the 3 test versions.

Image

I didn't think about the backwards compat issue... Just let me know which you think is best.

Alan

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Re: XR8 rx telemetary sensors

Post by aadamson » Wed Oct 23, 2013 8:31 pm

You know what... let's just roll this back to a 3 pin there... its no big deal and it serves a benefit based upon your comments... what I get for engineering on the fly :)..

Alan

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Re: XR8 rx telemetary sensors

Post by aadamson » Wed Oct 23, 2013 8:50 pm

Final version here...

Image

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Re: XR8 rx telemetary sensors

Post by ShowMaster » Wed Oct 23, 2013 9:13 pm

I want 4!

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Re: XR8 rx telemetary sensors

Post by aadamson » Wed Oct 23, 2013 9:21 pm

Not that big of deal and they don't hurt anything, but all but one of those ground vias can be removed :).... Ah, I'm sure there will be a v2 of this board :)...

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Re: XR8 rx telemetary sensors

Post by rdeanchurch » Wed Oct 23, 2013 11:03 pm

Based on rcGroups and here, the intereset is certainly there for a run of these.

Thanks Mike and Alan

Looking forward to a buy.
I have parts on order but doubt my soldering and debug skills, I'll gladly buy.
Dean
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Re: XR8 rx telemetary sensors

Post by aadamson » Thu Oct 24, 2013 2:55 pm

Mike,

Can you give me the 2 resistor values for a 3S and 4S battery configuration? Not sure what scaling you need internal in software so figured you'd know the values easiest... On another project that I work on that uses an stm32 as the flight controller and does battery detection, we use a 1.5k and 10k. But that's all scaled different so I don't think those are the right values?

Thanks,
Alan

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MikeB
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Re: XR8 rx telemetary sensors

Post by MikeB » Thu Oct 24, 2013 4:06 pm

3S, max voltage 12.6, I use 3K3 and 10K: measures up to 13.3V.
4S, max voltage 16.8, I'd suggest 3K3 and 15K: measures up to 18.3V.

Using 3K3 for the lower resistor is very handy as the full scale voltage is 3.3V.

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Re: XR8 rx telemetary sensors

Post by ShowMaster » Sat Oct 26, 2013 11:56 pm

I got all the parts now to build Mikes A2 circuit.
What's the progress like on the SMD version?

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Re: XR8 rx telemetary sensors

Post by aadamson » Sun Oct 27, 2013 12:02 am

I have everything on order, I should see boards in about a week, maybe smidge less. And parts kits should be here monday. I'm ready to make them as soon as I get everything... Stencil should be here just before the boards...

I ordered 30 of everything plus a couple to test with....

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Re: XR8 rx telemetary sensors

Post by ShowMaster » Sun Oct 27, 2013 2:14 am

aadamson wrote:I have everything on order, I should see boards in about a week, maybe smidge less. And parts kits should be here monday. I'm ready to make them as soon as I get everything... Stencil should be here just before the boards...

I ordered 30 of everything plus a couple to test with....
So how do we reserve and pay you so your investment is covered?
I need at least 2 but can commit to 4.

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Re: XR8 rx telemetary sensors

Post by aadamson » Sun Oct 27, 2013 2:24 am

Just hang tight.... I don't like to take money until I know everything works :)...

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Re: XR8 rx telemetary sensors

Post by hageha » Sun Oct 27, 2013 6:17 pm

If we e.g. want to measure a LiPo with BEC, the Grounds should be separated!
Otherwise, we have the same game as in the simple voltage dividers.

Here is a
simple, one-sided, onelayer, homemade version with balancer plug.
With pre-programmed ATtiny.
http://www.ebay.de/itm/350903644351?ssP ... 454wt_1265
Attachments
X8RAnalogSensor.JPG
Last edited by hageha on Mon Oct 28, 2013 7:58 pm, edited 1 time in total.

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Re: XR8 rx telemetary sensors

Post by aadamson » Sun Oct 27, 2013 9:24 pm

hageha wrote:If we e.g. want to measure a LiPo with BEC, the Grounds should be separated!
Otherwise, we have the same game as in the simple voltage dividers.

Here is a
simple, one-sided, onelayer, homemade version with balancer plug.
With pre-programmed ATtiny.
http://www.ebay.de/itm/350903644351?ssP ... 454wt_1265
I'm not even sure I understand what you are saying...

LIPO"s dont' have BEC's BEC's are separate devices. The link you referenced as a homemade version with balancer plug is an ISP programmer for an AVR that you can buy off ebay.

The device we are working with supports not only direct connection to a LIPO +/-, but also supports connection to the FBVS-01 which already has the voltage divider on it. Both require a connection to the + high voltage and the - ground, same for the FBVS-01. It is designed to plug into the X8R s.port connector which has V+, Ground, and serial s.port. The other side of the device needs to sense voltage via a voltage divider or the FBVS-01. I suppose that the ground is really unneeded on the LIPO side of things, but if someone wants they can pull the black wire. I suspect most people will plug in via JST or someother 2 pin connector the LIPO +/- and because the FBVS has a ground on that side we supported a pin configuration that makes it simple to plug and play.

Am I missing something?

Alan

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Re: XR8 rx telemetary sensors

Post by hageha » Mon Oct 28, 2013 3:13 pm

The link shows a possible tool to program a ATTiny outside the board!
In this way, can be omitted in favor of the board size of the ISP plug.

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Re: XR8 rx telemetary sensors

Post by aadamson » Fri Nov 01, 2013 8:30 pm

All, I got shipping notice on the prototype and first batch of boards today... I should see them monday I think... I need to get a few through hole resistors ordered I guess... all the rest I have here already :)...

Mike, any changes to the tiny code? And did you put it on googlecode or other?

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Re: XR8 rx telemetary sensors

Post by aadamson » Fri Nov 01, 2013 8:46 pm

MikeB wrote:3S, max voltage 12.6, I use 3K3 and 10K: measures up to 13.3V.
4S, max voltage 16.8, I'd suggest 3K3 and 15K: measures up to 18.3V.

Using 3K3 for the lower resistor is very handy as the full scale voltage is 3.3V.

Mike.
Mike, got a question...

*what if* we got with the 4S parameters *always*... I assume you can scale the results in the TX to show the correct voltage? And if we match the numbers that the frsky module support - highest voltage of 19.8... if you had up to that plugged in the ADC would be seeing a value greater than it's reference... what do you do if that happens... will it just show max value until it ultimately drops down to below 18.3v?

I'm just wanting to only have to stuff one set of resistors (or someone can remove one and replace it with a jumper to use the external lead from frsky) and right now that's looking like the 3k3 and 15k versions... Can this support 4s and below with obviously lower precision?

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Re: XR8 rx telemetary sensors

Post by MikeB » Fri Nov 01, 2013 9:17 pm

No changes to the code. No, I haven't made a repository for it yet, need time, been doing other things!

With the 3S values, you have a resolution of around 0.05V, with the 4S values, the resolution is around 0.07V.

If you go over the reference, you just get a max. reading. If you go too far over, you will forward bias the protection diode, should be OK with enough series resistance.

What I could do is enable a pull up resistor on pin 5, then we could allow a jumper on the ISP header to pull this pin to ground. Fit the resistors for 4S.
No jumper would mean use the input as 4S.
Jumper fitted would mean scale for 3S.

This could work as we actually have a 10-bit A2D, but are really only using, for compatibility, as 8-bit. With the jumper fitted, we read the full 10-bit value, then scale it as needed (*183/133/4?) onto an 8-bit result. This way we could get the better resolution for 3S from the same resistors.

I'll see what I can do, although I have a busy weekend this weekend.

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Re: XR8 rx telemetary sensors

Post by aadamson » Fri Nov 01, 2013 9:21 pm

Thanks Mike, that sounds like a perfect idea... I won't have them together til mid week anyway, and I want to test them first before I build the first 30. Just tell me the *easy pins* that you'd want to use on the header and we'll do it... I'll built for 4S as you referenced resistor pairs.

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Re: XR8 rx telemetary sensors

Post by MikeB » Fri Nov 01, 2013 9:36 pm

Just created:
http://code.google.com/p/x8r-analog/

The link would go between pins 4 and 6 on the ISP header, pin 4 goes to pin 5 of the 'tiny and pin 6 is ground.

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Re: XR8 rx telemetary sensors

Post by aadamson » Fri Nov 01, 2013 9:39 pm

Thanks Mike, I'll plan accordingly, just as able let me know what you've code to support that... I can test everything else without... I'll just factor accordingly.

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Re: XR8 rx telemetary sensors

Post by MikeB » Fri Nov 01, 2013 11:18 pm

I've put some code together, I'll test it tomorrow if I get time.
18.3 / 13.3 = 1.37594
11 / 8 = 1.375
So all I need to do is scale the A2D value by 11/8 and adjust to 8 bits.
It might be a fraction of 1% out, but that is better than the resistor tolerance and can be corrected by the calibration in the Tx.

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Re: XR8 rx telemetary sensors

Post by aadamson » Fri Nov 01, 2013 11:32 pm

MikeB wrote:I've put some code together, I'll test it tomorrow if I get time.
18.3 / 13.3 = 1.37594
11 / 8 = 1.375
So all I need to do is scale the A2D value by 11/8 and adjust to 8 bits.
It might be a fraction of 1% out, but that is better than the resistor tolerance and can be corrected by the calibration in the Tx.

Mike.
yes, true enough and I'll get pth resistors ordered for the 3k3, 15k flavors...

Oh, and thanks Mike for you contributions.


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