3DR radios, telemetry discussion and help

[MikeyDSlagle]

So Santa brought me a 3DR radio for Christmas. I know this can hook up to an Eggtimer, Quark, and RRC3. I am looking into that and will work the details with Chris or Jim when I get to that.

For now I just want to play with the thing and get it set up. I had a USB cable lying around that I should be able to use to supply the 5 volts to the "Air" unit. And of course power to the Ground is via USB.


Here are the specs I found for a 3DR radio.
Power
Supply voltage: 3.7-6 VDC (from USB or DF13)
Transmit current: 100 mA at 30 dBm
Receive current: 25 mA
Serial interface: 3.3 V UART

I found some simple boards for about a dollar each. One has output of 5 volts at 500 Ma, the other is 800 mA. Yes I know, why not opt for the larger one and be done with it? I like the layout and formfactor of the 500 Ma better. Adjustable ones can be found all the way up to 3 amps, but I don't think that would be necessary. Either of these boards should run it just fine from a 2S or 9v battery?

I need to do some heavy updates on my computer in order to get Mission Planner or Q Ground Control to work. So I will have to come back to all that.

Mikey D

 

[tHoagland]

I'm using these radios for various UAV projects and they seem pretty stable and easy to setup. If you want to power one of these with a 2S or 9V battery, I'd look at using a BEC. I've had luck with this one, for other applications, in the past.

US Ship Hobbywing 5V/6V 3A Switch-mode UBEC, Max 5A Lowest RF https://www.amazon.com/dp/B008ZNWOYY/?tag=skimlinks_replacement-20

 

[MikeyDSlagle]

Thanks.
I didn't know what the heck that thing was, I had to research it. From what I read it looks like a switching power supply with a fancy R/C term for it, but I could be wrong. There is probably more to it that I'm not seeing.

Something like this is what I had in mind:
https://www.amazon.com/gp/product/B01N1I1LXH/?tag=skimlinks_replacement-20

 

[mikec]

Switching BECs for R/C typically supply enough current to drive servos under heavy load. Your radio will probably be fine with the linear regulators you found on Amazon, since they don't need a lot of current. A switching BEC will be more efficient, though.

 

[tHoagland]

Switching BECs for R/C typically supply enough current to drive servos under heavy load. Your radio will probably be fine with the linear regulators you found on Amazon, since they don't need a lot of current. A switching BEC will be more efficient, though.

What he said....

That said, I like those little boards you found and they have made it to my Amazon cart

 

[MikeyDSlagle]

Switching BECs for R/C typically supply enough current to drive servos under heavy load. Your radio will probably be fine with the linear regulators you found on Amazon, since they don't need a lot of current. A switching BEC will be more efficient, though.

Good deal.

What he said....

That said, I like those little boards you found and they have made it to my Amazon cart

LOL Amazing how things do that. Glad I could enable, I mean help. These are the ones I am leaning toward. I like the form factor better:
https://www.getfpv.com/diatone-5v-5...MI8cXuk_aw2AIVj9lkCh0r1wEFEAQYAyABEgKw4fD_BwE
I can probably dig around on that site and come up with enough stuff to qualify for free shipping.

Amazon has them for 10 bucks a piece.

 

[OverTheTop]

I didn't know what the heck that thing was, I had to research it. From what I read it looks like a switching power supply with a fancy R/C term for it, but I could be wrong.

Exactly.

SBEC units are more efficient than linear regs, as has been said. That means you get more life out of the same size battery. You can even get tiny 1A and 2A versions that would be much lighter and more suited to the 3DR radio setup. The PCB for those are about 1/2" x 1/2".

 

[MikeyDSlagle]

Okay, this may seem a silly question, but referring to the BEC referred to in post #2. Is that green ring some sort of noise filter? Like I say, never heard of a BEC before today.

And I keep reading these "loud" and have "noise". I understand (mostly) noise and such, I'm guessing since these are made for R/C then the noise problem has been dealt with. Wouldn't want anything jacking with my altimeters. Do the simple linear regs produce less noise?

 

[OverTheTop]

BEC (battery eliminator circuit) is usually linear. SBEC is switch-mode and chops up the high voltage to make it lower (typically). If an SBEC is not done properly it can emit more EMI (electromagnetic interference) but if designed properly the can quite happily coexist with sensitive electionics. I have a design that has a 5A 24V switchmode converter sharing the PCB with a microvolt sensitive analog front-end. Most of the SBECs you will find are designed for the RC crowd. If a company had a product that produced interference with the receivers they would have customers leaving them in droves. I have no hesitation in fitting a SBEC to a rocket if needed. The answer is to GROUND TEST THE SYSTEM.

The ferrite toroid on the wires keeps any electrical noise from the SBEC getting along the wires (antennas!) and radiating out into other electronics. Sometimes not needed, sometimes needed. Think of the toriod tying the two wires together so any signals going out on once preferably want to come back on the other.

 

[woferry]

Okay, this may seem a silly question, but referring to the BEC referred to in post #2. Is that green ring some sort of noise filter? Like I say, never heard of a BEC before today.

Yes, it's commonly referred to as a choke. Does the same thing as those 'bulges' you often see at one or both ends of computer cords (data cords and/or power cords), it suppresses high-frequency noise that may be generated by something, which would otherwise continue down the wires, using them as an antenna to radiate noise outwards and/or couple it directly into the next thing down the line. They're frequency-dependent resistors (known as inductors), at higher frequencies they appear more resistive, so they block higher frequencies while having less of an impact on lower frequencies. The number of 'turns' (wire loops through the toroid) affects the inductance, which is why you'll sometimes see those cable bulges have the cable loop through them a second time (saves them from having to make the bulge twice as long, roughly speaking).

And I keep reading these "loud" and have "noise". I understand (mostly) noise and such, I'm guessing since these are made for R/C then the noise problem has been dealt with. Wouldn't want anything jacking with my altimeters. Do the simple linear regs produce less noise?

In the world of electronics, much as everything else, there are trade-offs. The two main types of voltage converters are linear regulators and switching regulators. Linear regulators produce less noise, but are effectively resistors. Current-in is current-out, all they do is reduce the voltage. So if you're turning a 2S battery into 5V you're converting ~7-8.4V into 5V at the current being drawn by the load, and all of that extra power (P = V • I) is being burned in the linear itself. So the linear can get hot depending on how much current is drawn and the delta in the input & output voltages, this is why linears typically have lower maximum currents, because the inefficiency produces more heat and there's only so much heat they can handle without adding heatsinks, etc. Switchers (ignoring some inherent loss that depends on the design and parts used) are power-in-power-out devices, so they can be much more efficient than linear regulators, but, as the name suggests, they do this via switches (MOSFETs typically), which introduces ripple (noise) in the output voltage because some part of the time they're 'charging' the output from the input and the rest of the time they aren't so the output is dropping (this switched load can introduce noise back into the sourced voltage as well). The choke doesn't eliminate all of this noise (they're only effective at high frequencies, lower-frequency noise is reduced using capacitors or by increasing the frequency that the switching occurs [which reduces the efficiency due to dynamic losses]), but it's a quick way to tackle the higher frequencies. Another common trade-off is that switchers often require a larger delta between the input and output voltage to work properly, while linears can often deal with a smaller delta (they're commonly referred to as LDOs, Low Drop-Out regulators, the drop-out voltage being the minimum delta between the input and output).

I've used the same UBEC pictured in post #2, to power a Raspberry Pi Zero to be flown as a camera / data recorder (haven't flown it yet). Works well to power the Pi, though I haven't tested it in a noise-sensitive environment yet. In my case I cut the shrink wrap back a bit and unsoldered the jumper block, just sorting those two pins together on the board, to reduce the size a bit and to ensure the jumper didn't come out, as the output will malfunction (and likely destroy anything down-stream of it) should that jumper ever come off during flight. The Pi expects 5V so I'd never need the 6V option, anyway. I'd suggest at least gluing the jumper in place, or removing the jumper and putting a good solder blob between the pins instead, or removing it entirely and shorting on the PCB as I did, depending on your skill and willingness to hack up electronics.

 

[ksaves2]

Have you looked at this thread yet? https://www.rocketryforum.com/showthread.php?141685-25-GPS-Solution

I ran out of time and used a 1amp 5V voltage regulator https://www.pololu.com/category/84/regulators-and-power-supplies to feed the radio and the GPS chipset. You get what you pay for when investing in a GPS. I used a Ublox chipset -8N and the Ucenter utility. When I tried to shrink tube the GPS on the radio, the GPS suffered an attenuation of the satellite signal. It was worse on the 433Mhz radios than the 900Mhz jobs. Read the entire thread above and it goes into programming and recovery of the settings on the "airborne" tracker if one screws up the settings. If I kept the GPS a few inches away from the radio on a cable, it was fine.

I didn't get around to testing the ground unit as a "dedicated" receiver and the airborne unit as a "dedicated" tracker. The fact that a 2-way link is maintained I suspect there may be some decreased range as opposed to some of the dedicated rocket
trackers out there. You might want to read the programming page on the 3DR and see if the settings might be optimized to improve the range. DO NOT change your 9600bps communication speed or you'll have to reset the rig with a USB serial card
like shown in the thread. Kurt

 

[MikeyDSlagle]

Good info guys. I think I am going to grab a few of the linears and try them first. I'll see how much run time I can get out of a standard 9 volt and one of my 2S LiPos. And see how hot the linear gets. Then may step up to the BEC later if I need to.

I did look at the thread you mentioned. Well I actually followed it for quite a while. Thought I might would try it. Then everything started getting way out of my know-how and progress slowed to a crawl at one time, I simply stopped following. I'll peek back at it again one day.

I don't really need this for tracking. I have an Eggfinder for that. I just wanted a 3DR to play around with and get real time speed and altitude. It's not really necessary as I can get all that info after touch down, but it's pretty cool tech (to me) and I want to play around with it.

As far as the programming page on the 3DR, you talking about in Mission Planner or something similar?

 

[ksaves2]

No, not MP. There is programmer for the 3DR alone. I think the link is in that thread. You will certainly have to be familiar with a lot of the discussion that went on in that thread in order to be able to use these radios effectively. That was the learning curve I had to climb in order to get some rudimentary use out of them. It's not easy. Also the cost of these devices have gone up since the start of that thread. Kurt

 

[MikeyDSlagle]

Could you throw me a bone? All I am seeing is reference to MP and U-Center. But I'll keep looking. I am gonna read back through the thread when I get time. It's quite lengthy now.

*Edit: Found it by sheer chance. Someone mentioned a 3dr tool and I finally found it on a page from a google search.:

https://www.ardupilot.co.uk/ardupilot-software.html
https://vps.oborne.me/3drradioconfig.zip


I think this is where I dropped off last time: LOL

Thank you. Folks this is really suckee. If you don't have any hacking experience stay away until this thread gets easier. I was able to get the left side of the screen to come up with ecarsons instructions.
Thanks. Couldn't get the right side to come up. I gave up R/C years ago with the gold Futaba transmitters as I originally had a flying field in my back yard. Hacking this drone stuff is hard for the neophyte.
going to shutdown and start over. I don't have a GPS attached yet and just trying to get the programming software to connect. Again, I'm a total neophyte here myself. Kurt Savegnago

For anyone who thinks they can save money and time with this modality, stay away unless they are totally familiar with the drone hardware.
I was able to get the radio to connect once to a Winblows 7 home premium system. Close but no cigar. I will continue to keep working with it
because 500mW on the 70cm band with an NMEA tracker should be very useful. The Ham APRS stuff comes across once every 5 seconds and will
get one's rocket back but a little more Rf output will help for live tracking. Again, unless you are familar with this stuff, don't waste the $20.00 or more
until morons like me can get it up. I hate when others say it's easy but in reality if one isn't in the know, it can be a challenge. Kurt

 

[ksaves2]

You got the 3dr programmer up there that I was talking about. Just use the radio programmer not MP. Sorry I didn't remember the link. Go to the Ublox website
And look for the u - Center utility it's out in the open. Be aware that this works only with the u-blox GPS chipsets and you need to get a Serial USB interface board. Make sure it is 5V. This is only needed if you wish to monitor the performance of the GPS chipset that you're using. It is also used to change the parameters of the u-blox GPS chipset that you are using. You can also take the strings off the receiver and pipe them through U-center and you can see the tracker on the map and do various manipulations with the data. I have a picture of the USB serial board on that other thread. U-center can reprogram a Ublox GPS or it can monitor the strings (and signal strength for that matter.). Please be aware that only the top dollar GPS chips are completely
programmable. The $7 to $25 chips one can probably only change the Port speed.

With this discussion of voltage regulators, part of my problem might be due to the unit I chose and I might try to seek out a battery Eliminator circuit and experiment with that. It might be quieter though it might be bulkier to make a slightly larger package. The small cables provided don't lend themselves to the addition of a toroid very easily. Kurt

 

[ksaves2]

What the hay. I'm going to try one of those BEC and see what it does as far as performance. If I could shrink tube it to the radio and the GPS signal is not interfered with, this might be a reasonable route to go.
Only problem I see potentially is the Chinese (at least according to the FPV blogs) grossly over estimate
the power output of these things. Also it might be easy to convert to get the data output like altitude feed over the air but I don't find that enlightening. Once one finds the rocket they can always download that data so I doesn't matter. Kurt

 

[MikeyDSlagle]

Revisiting this:

I ordered me a few small linear regulator boards. Small as in about the size of the bottom of a 9volt battery. I have a few days off and hope to get to play around with em.

More questions:
I plan to fly the 3DR connected to my RRC3. Sharing the same board will be an EggFinder with the wire whip antenna. The 3DR and EggFinder antennas will be about 1.5" apart, running parallel. Will this cause problems? Should I move one to another location perhaps farther into the nose cone to where they won't be parallel?

Once all is up an running and I actually receive data from the 3DR/RRC3, what the heck do I do with it? I need a device to look at the data obviously. Available to me is a Galaxy S6 Active, Kindle Fire and an older Laptop. Software recommendations would be super helpful here. Is this where Mission Planner comes into play? I would like to see the speed and altitude in real time of course. Turning it into audio would be even better, but I know that is unlikely.

 

[OverTheTop]

The 3DR and EggFinder antennas will be about 1.5" apart, running parallel. Will this cause problems?

Ground test. That's the only way to be certain.

Keep the antennas as far apart as possible. Consider dialing the Tx power of the 3DR down a bit if you are not going to much altitude. Less power means less chance of interference.

Parallel my be worse than orthogonal (right-angles). Range test on the ground to get a feel for which is better for the two antennas. They are working in near-field mods since they are so close, so testing is likely the shortest answer you will get.

 

[cerving]

Chances are that the two won't interfere with each other too much, the Eggfinder only broadcasts about 10% of the time and it's on one channel. If you go into Mission Planner and play with the settings on the 3DR you can probably avoid that channel altogether... I'd create a 250 KHz guard band on either end to be safe.

 

[MikeyDSlagle]

Ground test. That's the only way to be certain.

Keep the antennas as far apart as possible. Consider dialing the Tx power of the 3DR down a bit if you are not going to much altitude. Less power means less chance of interference.

Parallel my be worse than orthogonal (right-angles). Range test on the ground to get a feel for which is better for the two antennas. They are working in near-field mods since they are so close, so testing is likely the shortest answer you will get.

Gotcha. I have lots of real estate in the nose cone to play with. I could even put the EggFinder elsewhere in the rocket if I have to.

Chances are that the two won't interfere with each other too much, the Eggfinder only broadcasts about 10% of the time and it's on one channel. If you go into Mission Planner and play with the settings on the 3DR you can probably avoid that channel altogether... I'd create a 250 KHz guard band on either end to be safe.

Thanks for chiming in Chris. I probably can lengthen the bay enough to avoid them being parallel. I have to get the radio out and play with it some more to fully understand the "guard band". I think I got it but just playing around with the software will help me out. I have (probably too) many projects in the works right now and a few are new things I am trying.

 

[ksaves2]

It seems to me the 3DR radios have to have a two way link to work and has the potential to cut down their range. There was something on one of the setup sites that the ground station could be setup for receive only but I don't know
if that would make much difference. It would be nice for this to be put to the test as I've read where some copter guys did some ground testing with these things and it really wasn't that impressive.

A fellow here posted he got decent service for GPS location but I wouldn't trust it for something that's hitting up high or far. If you're trying to get live data from an altimeter that will be easy to see with the last altitude you got a data packet and
if flying with an EggFinder correlate that with distance from the receive station. Kurt

 

[MikeyDSlagle]

It seems to me the 3DR radios have to have a two way link to work and has the potential to cut down their range. There was something on one of the setup sites that the ground station could be setup for receive only but I don't know
if that would make much difference. It would be nice for this to be put to the test as I've read where some copter guys did some ground testing with these things and it really wasn't that impressive.

A fellow here posted he got decent service for GPS location but I wouldn't trust it for something that's hitting up high or far. If you're trying to get live data from an altimeter that will be easy to see with the last altitude you got a data packet and
if flying with an EggFinder correlate that with distance from the receive station. Kurt

"He is trying to tell me something, I just know it." ~Marlin, Finding Nemo LOL You are talking about finding max range? If I can get this all figured before next months launch I can test it out with my Eggfinder and see.

So I am finally getting my radios to connect and configure through Sik Radio Config. A lot of stuff makes a little more sense now that I can actually see the settings. But I want to double check I have it right. I plug in the ground unit to the USB on my computer and I only have to power up the aerial unit - red and black. Yes? For programming. I know when it goes into use I will hook all the wires up.

So:
Dial down the power. Check. For testing I'll drop it down to 14 which is 25 mW. I won't go very high testing it.

Air Speed. Am I thinking correctly here? The Eggtimer talks to the 3DR at 19,200 baud or 19.2 Kbps. So is there any reason to set the air speed above 19, which is 19.2 Kbps? The lower this setting, the more range I can get...or so it says.

Min Freq / Max Freq. My EggFinder is set to 913. So I want to avoid that frequency correct? So using Chris' advice, I could set it at say 917000 and 922000, that would give me a 250 Khz guard band on each side?

# number of channels: 1 - 50. No clue what to do here. Advice?

Duty Cycle can be set to 0 to set it for receive only. I don't see this being an available setting if they have to talk both ways to work. So I will try that after I see everything is working.

Wishing I would have stayed in college....18 years ago. Ugh. Been that long..
I don't have a real good interface. It came with a tiny 4 pin connector that fits nothing I have so I hacked it up and have it wired to a hacked USB cable for now. Will have to come up with something for field testing. I get the connection issue sorted out I can hang it under the drone, put it in a box and let the baby run around with it, LOL, or stick it all in my Big Daddy and fly it in my yard.

 

[ksaves2]

The number of channels is just that. The number of channels that the radio skips through. I've been told the lower the number the more range but
lower speed of the link. The copter guys sometimes try to control everything through the 3DR. I suspect if they do that, they don't fly out of visual range.

For GPS or altimeter data a low speed might get more range. Personally, I'd do a ground test if one is going to use 25mW as I think that's too low.

College has nothing to do with this. One can diddle with this with the information to be had online. Some things like configuring for a one way link for maximum
range I haven't seen documented. If you find specifics, post a link. Kurt

 

[cerving]

Min Freq / Max Freq. My EggFinder is set to 913. So I want to avoid that frequency correct? So using Chris' advice, I could set it at say 917000 and 922000, that would give me a 250 Khz guard band on each side?

"913" is 913.000 kHz. +/- 250 kHz would be 912.750 MHz through 913.250 MHz. If you start at 914.000 MHz just to be safe, you got almost 14 MHz to play with.

 

[MikeyDSlagle]

The number of channels is just that. The number of channels that the radio skips through. I've been told the lower the number the more range but
lower speed of the link. The copter guys sometimes try to control everything through the 3DR. I suspect if they do that, they don't fly out of visual range.

For GPS or altimeter data a low speed might get more range. Personally, I'd do a ground test if one is going to use 25mW as I think that's too low.

College has nothing to do with this. One can diddle with this with the information to be had online. Some things like configuring for a one way link for maximum
range I haven't seen documented. If you find specifics, post a link. Kurt

The college comment...I was going to Devry studying Electronics Engineering Technology. That sort of thing would go a long way with all the nomenclature and specifics doing this stuff.

"913" is 913.000 kHz. +/- 250 kHz would be 912.750 MHz through 913.250 MHz. If you start at 914.000 MHz just to be safe, you got almost 14 MHz to play with.

Okay, that is what I was thinking. I can only program in whole MHz numbers, which is where I got confused.

I just sent you an email Chris, got a problem with a Quark.

I am building the Quark to use for ground testing and first flights and what not. Hit a snag while building my Quark but I am making a little headway getting everything else all sorted out. Thanks for all the input guys. Much appreciated.

Now that I think about it. I have a Quark mounted in my Little John nose cone. Setup is flight proven. It is set up for an Eggfinder too and I may can get the 3DR on the back side of the board, opposite the EggFinder, which would also test the parallel antennas. Just have to pull the Quark and solder some wires on it for the TX and GRD wires. It's already set up for 2 LiPos as well. Yeah, that is my best bet as of now.

 

[MikeyDSlagle]

I have my radio configured through the 3dr configuration utility. Now how do I capture and view the real time data? I try connecting through mission planner and get "no heartbeats" message.

I have google searched for 2 days. Nothing has helped. Do I have to have data running through the radio to make heartbeats? This is all new to me.

Is there another program other than MP? Chris mentions a terminal program in one of his manuals (Quark maybe?) I have TeraTerm for programming the Eggtimer but know nothing about how to use it.

 

[ksaves2]

You are using two radios right? I modified the receiver to use B/T modules and piped the NMEA strings to GPS Rocket Locator, Rocket Track or if using UBlox products UCenter: https://www.u-blox.com/en/product/u-center-windows.
Also, I picked up a receiver that one can plug directly through a computer via a micro USB cable.
Also please read that prior thread I tagged above in msg 11. There is a lot of groundwork laid out by many people. Be sure you have a USB/serial board in case you screw up the settings and need to get your airborne unit reprogrammed.
Trust me, I messed up mine royally. I didn't have success to the point of being able to fly a working unit but others there in that thead have and you could email a question or two. Kurt

 

[MikeyDSlagle]

Two radios. I have the air unit and the ground unit. Or do I need another ground unit? Can't think of why I would. I have the serial cable from Eggtimer that works to program the air unit. Had to do it twice already. And had to update the driver to do it the second time. Helps if the Tx and Rx pins are hooked up right as well.

Thank you for your input Kurt. I'll check back on that thread. I followed along for a good while but it difficult to piece together what everyone was talking about and the thread would veer off. It led to bluetooth which I don't need, centered around GPS, which I don't need. And uses a an established app for GPS data/location. Best I can tell, NMEA is GPS. There is nothing there that helps me connect the radio to MP or something similar and I haven't seen heartbeats mentioned. I'll read it more when I can.

This is all interesting to me but I am getting into programming and code and all that stuff which I know little about. I have found some serial decoders and loggers online but many require Python, libraries, unfamiliar file types... and all sorts of stuff I don't understand. Some to the point that I don't even know which file to download.

I thought this would be simpler than it is. LOL I'll get one of the Eggtimer devices wired up and see if anything comes through my terminal, then I may put a pin in this and get my Eggfinder LCD flashed and get the bluetooth module hooked up. Knowing how high the rocket is in real time doesn't help if I can't find the thing afterwards. I need to experiment with that before my next flight, and get my motors worked out to fly my Viper.

We'll see...