«

»

Calibrating the Skylark Tiny OSD 2 (current sensor)

I just had a nice conversation with Skylark on Skype. He walked me through the calibration procedure and we got it reading almost exactly the same as my multimeter. It looks like this should work. Here’s what we did:

You will need to have a multimeter inline between the battery and current sensor configured to read current. Disconnect the GPS receiver from the main OSD board and connect the USB cable in it’s place. Connect the USB cable to you PC, then power up the OSD and start the Skylark software. Verify that the hardware is connected, then we start the calibration:

  • Step 1 – Run the motor at a low speed, and take note if the current reading in amps on your multimeter. Enter this into box A
  • Step 2 – Click Read, and verify that the box to the right of the button has a value in it now.
  • Step 3 – Run the motor up to a higher speed, and enter this reading from your meter into box B.
  • Step 4 – Click Read, and again verify that the box to the right has a new value.
  • Step 5 – Click Set to write the new Bias and Scale values to the OSD.
  • Step 6 – You can click Read now to verify that the new values were written correctly. It should read the same values that you just wrote to it in step 5.

Reset the OSD now.

At this point you should be very close. The OSD should be showing close to your multimeter on your display. (goggles or LCD) Mine was reading about one amp high all across the throttle range.

  • Step 7 – With the throttle off and motor not running, make a note of the current shown on your meter. Mine was reading about 470mA, or 0.47A. Enter this into the Current Bias box up top in amps. (0.47 in my case), and click Set.

Now reset the OSD again, and your OSD should read pretty much exactly the same as your meter within a few mA. At this point I shut everything down, connected the GPS back to the OSD, and powered up again. I found that the OSD was reading just about 10-15mA low now, and thought maybe it’s the GPS’s load that’s making a difference. So I took note of the current shown on my meter with throttle at idle, then shut it all down, connected the USB cable again, and loaded the software. I then entered that new value (0.54A in my case) into the Current Bias field in Step 7, clicked Set, then powered everything off again. I connected the GPS again, powered everything up, and the OSD was again perfectly in sync with my multimeter. Success!

I will test fly it with these changes asap and report here, but I expect it to work fine now. Multiple restarts and testing shows it to be near perfect with my multimeter now, which it never was before calibration. Wish me luck!

Update – I flew a short flight today, Friday. (High winds!) The current displayed on screen seemed to be working fine in flight. When I landed the OSD said I used 755mAh from the battery. My charger put 770mAh back into it with a balance charge. MUCH better than before calibrating. Looks like the problem is solved! :)

Notice

Check the pingback link below for a really nice jig to make calibration the current/voltage much easier!

7 comments

1 ping

Skip to comment form

  1. Wayne Howarth

    Did this procedure, seemed to work until I reconnected everything and checked the OSD read-out against the In-Line amp meter. With no motor running all was good, but when I increased the throttle to slow idle (NAZA – M) the Amp meter read 1.45 amps and the OSD was now reporting 0.00 Amps. Increasing the throttle from that point didn’t seem to change the read-out.

    My Skylark TinyOSD III may not use the same process, I’m on Rev 2.9.

    Can you put me in touch with Skylark, I can’t seem to get anyones attention. I also have Skylarks converter board, TraceOSD and their AAT IV. I am having issue with them as well.

    1. Keith

      Hi, I haven’t tried with a Tiny 3, I don’t have one. I’m not sure what all changed on that one. If you can’t get in contact with Skylark through their website/email, the only other options I know of are Skype and the forums. Their Skype ID is “skylarkfpv”. They also have a forum on fpvlab, which you can find here – http://fpvlab.com/forums/forumdisplay.php?39-SkylarkFPV Even if they don’t reply there, maybe someone that’s calibrated a Tiny 3 can help on the forums. Good luck!

  2. Mordy

    Thanks so much for your effort, It work beautifully, I just followed the instructions as laid out, Current with 100mA my voltage is reading around .2 lower than actual but I like that as a margin.
    Very Cool Thanks

    1. Keith

      Thanks for the comment, glad to help! I love this OSD, I just put mine back in the air in my new Teksumo. One of my favorites for a simple OSD. :)

  3. CORNELIS

    Thanks for sharing the info, It was very informative. With the volt readings what do you do with these?
    Thanks Cornelis

    1. Keith

      To calibrate the voltage reading, you’ll really need a variable DC supply to connect to the current sensor so you can adjust the input to the high and low ends of the range you expect to see with your battery in flight, and use those values to calibrate it just like the current. For example with a 3S pack, I would do 9.5V and 12.5V in the two boxes, adjusting the voltage supplied to the current sensor accordingly.

  4. Eric

    Having issues with my dianmu. Skylark says it can be calibrated the same a tiny/trace, so ive been following these instructions. I just cant get consistent measurements, either the idle amperage is too high and the running amperage is close, or the idle amperage is close and the running amperage is too low. I’ve retried several times with no success, and when I try it with the GPS connected instead of the USB, the readings go even further off. It’s close-ish, but I need to be within at least 5% margin of error. Thanks so much for your help with this so far.

  1. ACEFPV » OSD Current/Voltage Sensor Calibration Jig

    [...] Click here to read my friend Keith’s instructions on calibrating a Skylark Tiny II current/vol… [...]

Leave a Reply

Your email address will not be published. Required fields are marked *