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Topic: Electromagnetic interference? (Read 4576 times) previous topic - next topic

exceleronsports

@Tom...

The 78 series regulators are actually DROK 090945 regulator components... couldn't figure out how to change the label in the schematic software.

https://www.amazon.com/DROK-Converter-Step-down-Transformer-Stabilizer/dp/B00IWOPS8K

I'm not sure what you mean by "caps" on the supply line.  The batteries are just simple battery packs like this for example:

https://www.amazon.com/CO-RODE-Battery-Holder-Wired-Switch/dp/B00VE7HBMS/ref=sr_1_2?s=electronics&ie=UTF8&qid=1471919014&sr=1-2&keywords=8+battery+pack

allanhurst

Earthed shielding - a metallic cover connected to 0v to ground em radiation from a source.  Wire mesh would be fine

Allan.

Wawa

#17
Aug 23, 2016, 04:43 am Last Edit: Aug 23, 2016, 04:49 am by Wawa
TomGeorge said "Definitely not a fritzy...." for a reason.
I could make heads nor tails of the power distribution.
Post#0 seems to be different from post#11.

Why are the 78xx regulators there. Are they for the two? GoPros.
An 78xx regulator has a dropout voltage of 1.5-2volt, so 4AA batteries in (< 6volt) might only be ~4volt out of the ?5volt regulator. Less if batteries go down. Starvation for the GoPros.

I see you use buck converters (bloody Fritzing). They might have a 1volt dropout. Not good to have 5-6volt in for 5volt out. The display also won't help battery life.

470k for the temp sensors? Shouldn't that be 4k7.

The circuit around Q2 doesn't make sense.

130ohm/100ohm and 200ohm/100ohm for measuring battery voltage? I would expect 100x those values.
12volt on a 200ohm/100ohm divider is also dangerous for the analogue pin.
Ratios suggest you measure battery voltage with default Aref. Not good.

Not sure how the Mega gets it's power. It is missing on the diagram.
With 8 batteries on V-in, you will loose half the power of the batteries.

How much current is drawn from the 5volt pin of the Mega. Does the regulator get warm.
How much is drawn from the 3.3volt pin.
Leo..

exceleronsports

#18
Aug 23, 2016, 04:57 am Last Edit: Aug 23, 2016, 05:08 am by exceleronsports
My apologies on the fritzy... I was already 99% done when I saw the message and worked on it for hours.... I figured this was better than the hand drawn.

The 78xx series are DROK regulators, see post 15.  The DROKs are used to get a regulated 5v USB output for the GoPros.

The 470k resistors are 4k7... I mislabeled the schematic.

The Q2 section is a PNP transitor switch.  If the Arduino 5v power shuts off (base), the piezo (actually not a piezo, but an audible alarm) sounds using the camera batteries as a power source.  Was having trouble retracing my soldering while I was doing the schematic.  Not sure if I drew it correctly, but it works in real life.

I'm not an expert on voltage dividers, but if you use the proper ratio, what's the harm?  12v in with a 2/1 ratio would give 4v out, no?

Mega is powered via barrel plug from the 12v batteries using the Mega's built in voltage regulator.


Wawa

#19
Aug 23, 2016, 06:58 am Last Edit: Aug 23, 2016, 07:00 am by Wawa
I'm not an expert on voltage dividers, but if you use the proper ratio, what's the harm?
12v in with a 2/1 ratio would give 4v out, no?

Mega is powered via barrel plug from the 12v batteries using the Mega's built in voltage regulator.
1) Take the 130:100 divider.
What happens if you remove power to the Mega (remove a battery).
Almost 3volt is on the analogue pin.
An Arduino pin shouldn't see more than VCC +0.5volt (= 0.5volt).
The pin could survive if current is limited (<=1mA), but fault current could be 20mA into the pin in this case.
This 130:100 divider also consumes ~26mA from the 6volt battery.
10k:13k would give the same result, is safe for the pin, and only uses 260uA.
The 100:200 divider needlessly consumes about 40mA.

2) Then half the capacity of that battery is wasted, and turned into heat.
A 5volt micro-power buck converter could double the run time.
You didn't say how much current is used by the devices that are powered from the Mega.
Too much (> ~200mA) could overheat the onboard regulator(s) and make them shut down.
A 5volt buck converter connected to the 5volt pin of the Mega (or the USB socket) would bypass the onboard 5volt regulator (not the 3.3volt regulator).
Leo..

Example of a micro-power regulator.
https://www.pololu.com/product/2843

exceleronsports

1)  Thanks for the info!  I'll get this changed.  You said  "10k:13k would give the same result" did you mean "13k:10k" ?  Would you recommend something like 110k:10k instead to get an 11/1 ratio would would bring the 6v down to 0.5v to be safer for the pins?

2)  I'm not sure on the current.  I'll have to measure that again to check.  I know the 12v input is wasteful and will likely be changing that, but I don't think this is related to our main issue.  We've had the 12v battery pack for other flights and it worked great.  My issue with GPS reception only arises when the camera battery packs are turned on.  Also, if I turn on the camera battery packs, but physically take the unit out of the payload box (away from the cameras), it will work fine.  Literally, the act of just putting the electronics into the payload box or not is what causes/replicates my issue.

arssant

1)  Thanks for the info!  I'll get this changed.  You said  "10k:13k would give the same result" did you mean "13k:10k" ?  Would you recommend something like 110k:10k instead to get an 11/1 ratio would would bring the 6v down to 0.5v to be safer for the pins?

2)  I'm not sure on the current.  I'll have to measure that again to check.  I know the 12v input is wasteful and will likely be changing that, but I don't think this is related to our main issue.  We've had the 12v battery pack for other flights and it worked great.  My issue with GPS reception only arises when the camera battery packs are turned on.  Also, if I turn on the camera battery packs, but physically take the unit out of the payload box (away from the cameras), it will work fine.  Literally, the act of just putting the electronics into the payload box or not is what causes/replicates my issue.
Hi.

You are not alone with gopro cam and GPS reception-interferences. issues.

5 secs of google for "camera interference GPS".

Gopro vs GPS

Solution: metallic enclosure for the gopro, acting as an Faraday box emp protection ? or as you describe, put the gopro far as possible from the gps unit.

exceleronsports

Thanks for this!  I had looked for GPS/camera interference, but most articles I read were related to interference coming from the camera's WiFi.  My camera doesn't have WiFi at all so I didn't think it would be an issue.  I'll try creating a faraday enclosure for the cameras to see if that helps.

arssant

Thanks for this!  I had looked for GPS/camera interference, but most articles I read were related to interference coming from the camera's WiFi.  My camera doesn't have WiFi at all so I didn't think it would be an issue.  I'll try creating a faraday enclosure for the cameras to see if that helps.
From 2 gopro users:

"The Garmin does not have a wifi network, I transfer data to/from it via USB cable. I don't have Wi-fi turned on on the GoPro whilst using it out on the bike."

" FYI the WiFi in the GoPro is dasabled."


So wifi or not, they have similar issues as you.

exceleronsports

Thanks!  I'll check this out tonight and see if it improves/resolves my issues!

raschemmel

This is all outside my area of expertise but the thing that seems to jump out at me is that you have a camera transmitting a signal and a GPS that presumably is trying to receive signals and the camera signal seems to be "swamping" (interfering ) with the GPS signal. Have you tried reprogramming it so the two alternate so the camera transmitter is turned off intermittently while acquiring GPS coordinates ? Would that arrangement work for you ?
Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

exceleronsports

The camera does not have a transmitter and doesn't do any transmitting.  It's just taking video and saving it to the onboard camera micro SD card.

dlloyd

#27
Aug 23, 2016, 09:21 pm Last Edit: Aug 23, 2016, 09:24 pm by dlloyd
I don't think its interference ... otherwise why does this work?
Quote
The tracker works perfectly when connected inside and/or outside of our payload box and with USB power input
Quote
The tracker works when inside the payload box with used batteries, nearing end-of-life
This suggests that there's a power problem with Vin at higher voltages, which prompted my previous reply. I would try a test with 5 fully charged batteries (7.5V) connected to Vin to see if the problems go away.

exceleronsports

#28
Aug 23, 2016, 09:27 pm Last Edit: Aug 23, 2016, 09:32 pm by exceleronsports
Quote
The tracker works perfectly when connected inside and/or outside of our payload box and with USB power input
No camera batteries running in this scenario, but you bring up a good point.  I'll try USB power on the Arduino and full batteries for the camera and see if I still see the issue.

Quote
The tracker works when inside the payload box with used batteries, nearing end-of-life
Could still suggest an interference issue, no?  As the batteries near end of life their power is less and thus their interference would be less too?  I'll definitely try your idea, though. 

Lots of good ideas for testing coming out of this topic, so very appreciative of all the responses so far!  I was running out of ideas for testing so always nice to get different perspectives.

mauried

Are there any switch mode power supplies being used for voltage conversion.?
Whilst its not normal for switch mode power supplies to generate L band hash, if you cant find
any other problem try temporarily substituting the switch modes with linear regulators.

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