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Old Mar 05, 2014, 11:32 PM
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That RFM22B looks interesting, being as it is a transceiver could one be used as the transmitter as well as one for the receiver?

At 100mW output for the RFM22B it should have decent range on its own without amplification but there are fairly cheap modules on ebay available that output from 5 to 10 watts like this one. http://www.ebay.com/itm/M67799MA-430...item1c2f9f2c23

7.5 watts at 433MHz would have a ridiculous amount of range with even a half decent antenna!

Could the RFM22B directly replace the 7105 or does it work differently as far as communication with the micro goes?

Does PPM need to be converted in order to be transmitted or can PPM modulate a carrier frequency directly? If it can be directly transmitted, at what frequency does the PPM signal work at? (I'm feeling too lazy to hook up my 9x to my scope at the moment (I probably will anyway though))

Making a transmitter module from scratch would be pretty easy, the receiving bit would just be a bit more difficult. I have many crystals from 3MHz up to around 30MHz. I could hook up a circuit to run on a harmonic at something close to 100MHz but outside of the FM broadcast band and use a modified FM radio as an RX to send PPM if it isn't too difficult to program on the micros being as I have no clue at the moment how to do anything with them. I feel like it is a bit harder than Ruby or HTML. (I know a little bit in those) But I haven't looked at any code for them yet so I'm not sure.

There would be a lot of noise around 100MHz but it would be interesting to see if it would work and how far it could go.

I also noticed in the "DIY FlySky RF module" thread that there are schematics using an external crystal on the micro and some using the internal oscillator. What is the reasoning behind this, is there much of a benefit to using a crystal on the micro?

How much does the complete 7105 module weigh?

I just finished a little 3ch plane (tho rud ele) a couple days ago and test flew it yesterday. It has a 12 inch WS with an AUW of 32g so not that light but it flies decently. Made of balsa and Dollar Tree foam. I added a photo of it.

Will
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Old Mar 06, 2014, 06:39 PM
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New York
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yikes, what an EXCELLENT creation. that is MY kind of model plane. and those tiny hk servos are just about my favorites too. heres a thread where i strip them down to less than a gram: http://www.rcgroups.com/forums/showthread.php?t=1611336. also ive purchased quite a few just for the parts. that is one tiny pager motor.

that rf amp is cheap but that approach is not really my go-to solution for extending range. imo better antennas and lna are the key. not only cheaper but actually legal. speaking of which i dont think 100mhz is that great an idea either. true the lower frequencies increase range (BIG time), but in that case the original rc 72mhz would be even better. super long range fpv hounds know this. true the radios and rx are getting hard to find but they are still available if you look hard enough.

and yes, the ppm signal can be fed directly into those cheap 433mhz modules. but only if they have been converted to fm. that only takes a minute or two and costs pennies as seen in the link couple posts back. the only issue is what to use for tx because the ones that come with it are am only and almost useless range. my new idea is to use the silabs modules for the rx end and they dont cost much either. although ive not proven it yet i think range could be miles pairing those up.

regarding mcu crystals, they are 1000x more accurate than internal oscillator but for most applications not necessary. the crystal in that photo is for the 7105, not the tiny avr, and is an absolute requirement there. no tolerance for even a few parts per million frequency error in that application.
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Old Mar 06, 2014, 10:29 PM
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Thanks! It flies decently but I need to redo the elevator because it doesn't have enough downward throw. Any tips on using music wire springs for control surfaces? I'm using an inch or so of an old high E string from the last time I changed guitar strings a couple months ago. It is nice and springy but the foam isn't cooperating very well, thinking of making it in balsa instead but balsa is less forgiving when you crash.

Those HK5320's are fantastic! As soon as I started working with them I decided that those were going to be my servo of choice for all 2g servo needs. I need to order more, only have 5 including the ones on that plane.

I didn't even realize that a brushed motor could be that tiny! 4mm is incredible!

I have also found that those 10 dollar 3ch HK receivers work nicely on 1c lipo directly without an issue even though they are only rated down to 4 volts or so. Reliability isn't much of an issue with a little 30g slow flying plane, it can hardly hurt itself, never mind a person or building. The rx weight can also be brought down below 3.5g after removing the case and pin header.

The amp would be nice for the low power modules that only put out 10mW or so, the 7.5 watts is the max and can be lowered by varying the input being as it has a finite gain.

I could always just make a 72mhz module too. That would be nice and legal. Then I could use my T9x on 72mhz easily. On that note, what is the upper legal limit of output power on vhf and uhf without a license?

I realize that the crystal is for the 7105 in your application, I was talking about the one used with the mega8 in the other thread (photo link: http://static.rcgroups.net/forums/at...odule-XTAL.jpg) I don't see the benefit of the accuracy for that application.

I think now my current goal with the project is to get a micro working that has a PPM input and 4+ servo channels for the outputs. I think that might be doable on a tiny13. I could then use IR for ultra-micro indoor stuff and hook it up to any given radio system that I could come up with using the PPM from my T9x.

Will
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Old Mar 22, 2014, 05:10 AM
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Sorry if this is obvious... But I have been searching around and I cant seem to find the Arduino Sketch or .Hex for the ATiny13 with PPM output. They all seem to be labeled for the mega8 or other chips. Could someone point me in the right direction?
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Old Mar 26, 2014, 07:23 PM
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Quote:
Originally Posted by Curtisbeef
Hi Dave,
I have been reading alot of the threads about your DIY multiwii and FlySky stuff. Awesome work man.
I have been looking around and I cant seem to find the HEX or ino files for the Tiny13 with FlySky PPM. Could you point me in the right direction? I searched all over the threads...
Thanks in advance.
Curtis
the tiny13 was done in asm and not arduino so no sketch. and since it was done "for pay" its not open source. but it is one of my favorite chips. you can build 10 projects using t13 for the cost of one of the popular m328. so i will help with whatever you need to know to develop your own version. its not hard at all and you can learn a lot from midelics threads which do have lots of arduino sketches which should be easy to port:

http://www.rcgroups.com/forums/showthread.php?t=1921870

but i warn you its unlikely to implement in c or arduino in a chip with only 500 words so maybe roll up your sleeves and take a look at asm.

oops... i just noticed that you posted too. sorry i couldnt get back sooner, flooded with lots of other messages most from non-posters.
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Old Apr 01, 2014, 07:53 PM
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I'm somewhat of a noob in the rc world, so some of these questions might sound a bit stupid:

What's PPM?

I see you say you've got the price down to $9 for the helicopter. Let me summarize what I understand you describing:

ATMega8 for the controller
7105a for the rx
All wired up according to the assembly instructions in update 4/10/2013.
This would be connected to the "gils mega328 multiwii fc with tiny ppm soic8 rx chip on board"

What is this "multiwii fc"? Where do I get it? From your descriptions it seems that it has rx and an AVR build in? If it has all that, then why do I need to build an external rx?

All put together, this would replace the v939 controller board in your "$18 diy quadcopter" design.

Any errors? Any missing details?

Also, do I understand correctly that this 7105a module can also serve as a transmitter so I can use a second module with an ATTiny and a pair of joysticks for the transmitter? (I think Dave1993 has done this.)

Also, am I right that these module comply with the flysky/turnigy protocol and thus can be used with a transmitter such as this one for the wltoys v939:
http://www.banggood.com/Wholesale-WL...2-p-63784.html

Another question: How are you getting this down to $9? When I add up all the parts, it sums up to $10.74 not counting the multiwii fc which I'm guessing would cost at least $5. Would you mind posting your sources?

Code:
Item	$ each	QTY	$ Total
ATmega8	 $2.15 	1	 $2.15 
XL7105	 $3.27 	1	 $3.27 
motors	 $1.33 	4	 $5.32 

Final Total: $10.74
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Old Apr 02, 2014, 05:31 PM
RC beginner
New York
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HEY, what are you doing over here too? are you STALKING me? lol.

anyway, no stupid questions (not knowing is not a sin), only stupid answers. we got plenty of those here on the internet. hopefully not too many from me... at leat not UN-INTENTIONALLY. i do like to spit on the supermens capes.

Quote:
Originally Posted by TinyTree View Post
What's PPM?
Pulse Postion Modulation is the protocol that virtually all radio stick boards use to talk to the rf module. location of pulses in the frame carry the info and pulse width matters little. unlike PWM (servo) where its everything. google and wikipedia are your friends.

Quote:
Originally Posted by TinyTree View Post
ATMega8 for the controller
7105a for the rx
All wired up according to the assembly instructions in update 4/10/2013.
This would be connected to the "gils mega328 multiwii fc with tiny ppm soic8 rx chip on board"
actually there are 2 avr chips required for the entire setup. a tiny or mega to run the 7105 transceiver for a rx. a mega328 for the flight controller (fc) which controls motors from sensor data. in traditional multicopters these were separate boards but in the new toy copters its all combined into one small pcb that typically weighs about 1/10 as much. costs 10/th as much too. unfortunately many hotshot hobby snobs fail to recognize these a rc models.

by taking the diy route cost can be cut even more than the toy fc and using deadbug (not for the faint of heart) even further. not to mention weight which is now about 1% what it was.

Quote:
Originally Posted by TinyTree View Post
What is this "multiwii fc"? Where do I get it? From your descriptions it seems that it has rx and an AVR build in? If it has all that, then why do I need to build an external rx?
as mentioned historically fc and rx were separate products. this allows people to build copters that work with many different rc radio brands. "multiwii", called that because it used a gyro from wii motion plus, was the first diy unit and still most popular. it does not normally have a rx built-in but i fixed that. midelic went even further and connected the 7105 transceiver chip directly to the fc computer instead of having its own separate one. im not sure anybody got that to work. it had problems for me.

Quote:
Originally Posted by TinyTree View Post
All put together, this would replace the v939 controller board in your "$18 diy quadcopter" design.
yes. and potentially for lower cost and a lot less weight. and a LOT more work. unless your primary goal is diy fun and learning the recommendation is to start with the banggood board. its not like $12 will put you in the poorhouse but might get you started quicker. a good stepping stone if you move on.

Quote:
Originally Posted by TinyTree View Post
Also, do I understand correctly that this 7105a module can also serve as a transmitter so I can use a second module with an ATTiny and a pair of joysticks for the transmitter? (I think Dave1993 has done this.)
yes. and again midelic took it a step further and put up some excellent how-to threads on building not only flysky but towards a "universal" radio. at least the flysky tx part worked pretty good for me.

Quote:
Originally Posted by TinyTree View Post
Also, am I right that these module comply with the flysky/turnigy protocol and thus can be used with a transmitter such as this one for the wltoys v939
yes.

Quote:
Originally Posted by TinyTree View Post
Another question: How are you getting this down to $9
like i mentioned in your post in the other thread, you do it by shopping and buying more than one at a time. i dont mean a hundred but maybe 3 or 5. i dont have time to do complete set of links for every part for you but as an example:

http://www.ebay.com/itm/5PCS-IC-ATME...item1e88d3fc7c

notice this is about 1/3 what your "personal shopper' program came up with. imo those suck. nothing beats letting your own fingers do the walking. most of these parts even less on aliexpress but you lose the great ebay buyer protection. rc groups is another place to find great bargains but you do have to read the threads, granted some of them are HUMUNGOUS. good luck.
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Old Apr 02, 2014, 07:53 PM
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Nice price, shame that seller does not ship to the UK...

This one does thought

5PCS IC ATMEGA8A-AU TQFP-32 ATMEL NEW DATE CODE 12+

http://bit.ly/1mLycw8

I think I might have to order 1 lot from this seller just so that they are there if I need them.
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Old Apr 03, 2014, 06:38 PM
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New York
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ive placed literally over a hundred orders with gc last couple years. only couple problems and always made good. they are famous for specializing in mcus and similar ics and definitely among the best dealers in that area. ouyou sells lingerie, bracelets, and other stuff like that with a few chip listings sprinkled in. all these guys are selling refurbs but very well done and few problems like missing or warped pins.

my best internet deal ever was $.48 and around $.80 for m328 on aliexpress but out of a several dozen there were a few duds. much harder to deal with than ebay though because of language and support issues. sometimes (but not always) you do get what you pay for. worth the risk/benefit for me being in a good position to test with experience and jigs. however not so much for those starting out.
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Old Apr 19, 2014, 11:05 PM
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Thanks a lot for all your answers. I'll have to ponder them some other time since it's a bit to late at night for me to think straight.
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Old Apr 20, 2014, 11:14 AM
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I've searched this thread without any definite answers, whats the best way to increase range with an antenna on the 7105 modules?
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Old Apr 22, 2014, 07:01 PM
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depending on what you mean by "best" i think chopping off the crummy pcb piggy tail and replace with a dipole is a good compromise. to get really long range and coverage one might try one of those umbrealla or other cp the jesus guy pushes. or you could get really fancy and attach an sma connector for hooking up yagi or whatever (is there an echo in here? lol.).
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Old Apr 22, 2014, 07:42 PM
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I think "best" is best bang for your buck. I googled and didnt find much in the way of photos of people adding antennas to these boards. The folded back braid on coax wire seems like a simple dipole option. Any photos of how you do it?
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Old Apr 22, 2014, 09:58 PM
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You can use a sleeved dipole. You just need a copper tube to solder the braid onto. Hobbyking's cheap 9x receiver use them and I've successfully cannibalized one in the past for a TX module antenna.

Just cut the copper tube to the appropriate length for 2.4 (or whatever frequency you're using) and solder the shield braid to it. The copper tube maintains correct length better than merely folded sheilding. If you want you can then heatshrink the whole thing like what Hobbyking did.
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Old Yesterday, 05:17 PM
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yeah... listen to the 'man. he knows. i remember when frsky & flysky were babies and i explained one reason flysky had longer range than frsky was because of that antenna. frsky fanboys hit the ceiling. good thing theres no such thing as "cyber-lynching". i was actually extending the distance of d8r (there were no other rxs then) by transplanting one of those like in slebetmans photo. lots of scoffing until a few others tried it. now frsky has copied the flysky design onto all their high end rx.

so bottom line: brass tube is slightly better than folded back braid which is slightly better than simple dipole. personally in terms of cost, weight, and ease i prefer tacking on the couple 1" pieces of super thin wire. ymmv


ps heres a foto showing what it looks like w/o the shrink:

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