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Mr.RC-Cam

5.8GHz / 500mW Wireless A/V System:

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All set-up and ready to go in a Multiplex Funjet. This little plane can get some serious altitude. Transmitter looks great. Great job (as always) Thomas! Flight testing (with recorded video) hopefully Monday! :)

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And you shall have video! It will be entertaining and enlightening! :) I was getting over 70mph with it using an Astro 05 2 turn motor last week. Next thing I know, there's flames coming out the back (Serious flames. Just ask Ken - Kist2001)! I guess 60 amps (on a Castle 60) in the Florida heat with little airflow in a plane that's essentially an insulated beverage container was too much and the ESC went up in flames. The OSD started showing "ALERT" and before I knew it - flames! At any rate, it's repaired and the Astro 05 has been swapped out for a more sedate Astro 020. It should still be exciting!

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OK I have just managed to do 2 flights to compare the 100mW and 500mW TX's but the results are NOT what was expected. I noted the signal strength % using the new rc-cam rssi meter fitted to my auto tracking 14dBi patch. readings were taken every 500ft (horizontal) up to 5000ft range. At 500ft both were showing 98% as expected but at 5000ft the 500mW TX was at 63% and the 100mW was at 55%. That extra 8% is only worth about 1000ft at that range although it would be worth 2000ft at 10,000ft which I guessing from the numbers is about the max range of the 500mW TX using my RX setup.

Now I may just throw it all in the bin as at 5,500ft with the 500mW TX the signal dropped like a stone to between 35% and 0% and bounced about so no propper readings could be taken or indeed flying!

I have no idea what caused the odd drop as the batt and aerial were tested after and found to be fine. What is clear is that another flight with the 500mW TX needs to be flown. I will post the results when I find a day with low wind and a helper to take the readings...

OK I flew again even though the wind was gusting 20mph, I got out to 6000ft with a signal of 57% but then it just dropped like a stone again. Turning round didnt help again until I was at about 2000ft then it was a good picture. I thought maybe its getting hot but it was only warn to the touch after landing, very odd !

Terry

Edited by Terry

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Thanks for the report. My gut feeling in that the problem is not a heat issue because the Tx runs cooler than most and you are in a moderate climate. Maybe the sudden signal loss is due to a bad connection someplace? Possibly in the Tx itself, but it could be anywhere. Hopefully you can find the problem on the bench.

Just to give you a place to start, begin by resoldering all the Tx PCB connections. I know you are an experienced builder and have soldered the components with care (Terry personally built his 500mW Tx). But, my experience has been that problems like this are often a solder joint somewhere. Or, something you will notice (like a cracked inductor) while you carefully resolder the components. If this does not help then suspect everything, even those innocent looking connectors and cables that never cause any problems. :)

Also, is there any chance the problem is related to the 4-way diversity system? Just another thought (I tend to suspect everything when these kind of problems appear).

It is too bad that the max range couldn't be tempted on the flight. But despite the frustrations, when you had video, could you see any significant performance differences between the 100mW and 500mW Tx?

At 500ft both were showing 98% as expected but at 5000ft the 500mW TX was at 63% and the 100% was at 55%.

That sounds reasonable. The "8%" difference could easily mean 12dB or it could mean 4dB difference, or anything in between. It all depends where on the RSSI curve the measured voltage is at. So continue to use it for relative differences, rather than absolute data.

Edited by Mr.RC-Cam

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Also, is there any chance the problem is related to the 4-way diversity system?

No chance at all as I am using an auto tracking 14dBi patch of my own design, it has been used many times with the 100mW TX's and has always been perfect right out to over 1.5 miles.

Maybe the sudden signal loss is due to a bad connection someplace?

maybe but it seems odd that the signal has just dropped out twice now at a simular time and range I think I may have to get one of my other 500mW TX's fitted to the plane just to see.

That sounds reasonable. The "8%" difference could easily mean 12dB or it could mean 4dB difference, or anything in between. It all depends where on the RSSI curve the measured voltage is at.

I see your point but when plotted on a graff it shows it to be well under, can you confirm the 100mW TX's only give 100mW? I think we talked before about the fact they seem to perform better than expected, more like a 250mW TX to me.

Terry

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... maybe but it seems odd that the signal has just dropped out twice now at a simular time and range I think I may have to get one of my other 500mW TX's fitted to the plane just to see.

There's a reason for everything. Once you find the problem, observations like this will usually be fully explained.

By the way, what are you powering the Tx with? 2S, 3S, or ? What other things share this power?

... can you confirm the 100mW TX's only give 100mW? I think we talked before about the fact they seem to perform better than expected, more like a 250mW TX to me.

I can confirm that the 100mW Tx module is indeed no greater than 100mW. The 500mW module is as advertised too. So in a perfect world, you should see 2X range with the 500mW Tx.

Your sudden signal loss is a mystery, but hopefully not for long. Suspect everything, even the things it cannot be.

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Its powered by 2s which also powers the 131 as well, I know it was not designed to power a 5v camera and 3s would be better but it had to fall in line with my other gear as not to end up smoked like the first one. Do you see a problem with this?

Terry

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The 500mW Tx's DC-DC switcher supply will accommodate a 2S LiPO. But, since the current is quite high on 2S, you must ensure it is a healthy high capacity pack. Personally I would use a 3S, but I understand your camera is easier to power from the 2S.

So, let's talk a bit about the power system before you start the troubleshooting; I have some questions:

(1) Was the same 2S used on both flights that lost video?

(2) Was it/they fully charged before the flights?

(3) What is the rated mAH capacity?

(4) How many minutes into the flight before the video was lost?

(5) What is the current consumption of your camera?

(6) Since your camera requires 5VDC, exactly how are you getting it from the 2S Pack? LM7805, or something else?

(7) Do you use an OSD? If so, what voltage did it report on the 2S shortly before losing video?

(8) Anything else being powered by the 2S?

(9) What was the 2S voltage, fully loaded with the video system still turned on, at the end of the flight?

(10) Any other power system information that is worth mentioning?

And one more for good measure ...

(11) Did you see a short hairy fellow, with bad temper, tearing off the engine cowling when the problems appeared?

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1. no, I have 3 packs and use a fresh one each flight.

2. yes all packs are charged/topped up the same day as the flights

3. 900mAh, the osd voltage showed no problems

4. 15min, video was weak after this until about 2000ft range around 20min

5. not sure , its a KX131, now 11.30pm and going to bed soon so cant check

6. it uses the 5v from the TX

7. yes it was 7.3v

8. just the TX, osd and KX131

9. I think it was 7.1v , for sure over 7v as the osd flashes below 7.1v

10. dont think so

11. was that you ?

I guess I need to check the power used by the camera and osd but they are the same as used with the 100mW TX and have done 40min flights with plenty of room to spare. What can the switcher handle ?

Terry

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3. Compared to the 100mW Tx, the 500mW Tx is a current hog. Including the current from a typical 5V camera, your 2S/900 packs will provide about 45 minutes max run time at full charge. Perhaps less if you want a safe margin. So, don't linger too long in the pits.

5. Please measure the camera's current and report what you find. While at it, get the current to the entire video Tx/camera system. I suspect that at 7.0VDC, it will be up to 900mA.

6. Hmm. It wasn't designed to share its internal 5V power. But if the camera is low current, then it might be OK. However, a 3S pack would reduce the stress on the DC-DC system, especially with the extra load, so the 2S pack is not the ideal choice in your application. Worst case is you might need to use a separate 5VDC source for the camera.

7. That is a fine voltage.

9. Voltage is fine here too. However, power the A/V system with your variable bench supply and see if it works reliably all the way down to 6.0V. Hint: Measure the Tx's shared 5V with the camera connected and ensure it is still 5.0V at the low operating voltages. If this voltage sags then the DC-DC switcher is struggling with the low voltage source.

11. All I can say is that it was a bad hair day.

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OK I have not had time to dive too deep yet but I checked the current of the TX on its own with a 2s at 1.6A and a 3s at 3A, I was expecting the 3s to have a lower current. The 5v is rock solid so this is odd, what are the normal figures for 2s and 3s ?

Terry

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The Tx on its own, at 7.4V will be about 700mA and the 10.8V will be about 450mW. Either the strong RF from the Tx is affecting the meter (common issue with high powered RF) or something is assembled wrong. I would normally blame the RF for causing meter wackiness, my gut feeling is that in this case there may a problem that needs attention.

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I had the same thoughts but swapped to a dummy load so the RF should be very low, also the readings are solid. Something is wrong with the TX but the fact that the 5v is good makes me wonder what, I will have to find some spare time from somewhere, dose anyone know where I can get some spare time?

Terry

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Spare time -- what's that?

What is the current draw on your other 5.8GHz 500mW Tx?

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Hmmm just gone full circle, put a different amp meter on and the readings are ok so back to square one. I will try a flight with a 3s pack and see what happens.

Terry

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That is good to hear. Do the weird high currents return when the other meter is used again?

What is the current draw of the camera? {I'm still concerned about the load it is adding to the Tx's internal DC-DC supply.}

Does the DC-DC supply work all the way down to a 6.0V input voltage? {Need to confirm it is working correctly}

I still think that there there is a problem elsewhere. This power supply stuff was just a temporary detour before the actual troubleshooting. So there is a chance you will see the same loss of video problem again.

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Do the weird high currents return when the other meter is used again?

Yes they do, I think it maybe the switcher confusing my Fluke.

What is the current draw of the camera

150mA

Does the DC-DC supply work all the way down to a 6.0V input voltage?

yes, at 6v it give 4.99v and at 5.5v it gave 4.77v

I still think that there there is a problem elsewhere. This power supply stuff was just a temporary detour before the actual troubleshooting. So there is a chance you will see the same loss of video problem again.

me too, what is the chance of the switcher overheating and shutting down?

Terry

Edited by Terry

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... what is the chance of the switcher overheating and shutting down?

With the unexpected 150mA drawn by the 5V camera, this is possible. Especially on a 2S. Regardless of 2S/3S, there is definitely zero room for error in this situation.

After you have checked everything else (still could be a solder connection or other evilness), I suppose a test flight with a healthy 3S pack is in order. Bring a spotter! :)

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Just a quick update - The plane slipped from my hand during launch (Darn this girly arm!) and splashed down in a huge puddle of water. I've let all the components dry out for several days and tested them on the bench. All looks fine. Back in the plane and we'll try again!

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All my testing has come to a halt - I have a problem with my left eye as it is all 'blurry' and I can't focus properly and don't trust myself with flying.

Even soldering a servo lead is difficult enough at the moment.

Here are a couple of clips from my homebrewed 5.8 rig - works well.

'First light'

Made and fitted an LC filter for the supply line to the Rx

The rig I got from Thomas in a little r/c car...

I'll do some more as soon as my eye is better.

Nigel.

PS - how do you embed a video link (so it appears in a box as opposed to a hyperlink)??

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Made and fitted an LC filter for the supply line to the Rx

As you experienced, R/C switch-mode BEC's often have a lot of ripple, even those advertised as low noise. Sometimes the required LC filtering can be a burden. But it looks like you solved yours.

how do you embed a video link (so it appears in a box as opposed to a hyperlink)??

Normally you would click the Insert Media Icon, then enter the URL. But for some reason it is not working with Vimeo media (YouTube works fine).

Edited by Mr.RC-Cam
Fixed typos.

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Just had a quick test flight, no spotter availible as usual :( so I turned round at 8000ft out and 55% on the meter. No sign of the cutting out problem so looks like 3s has done the trick although it is a bit cooler today too.

Terry

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