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Old Oct 06, 2012, 05:47 AM
RC beginner
New York
Joined Oct 2008
6,054 Posts
Build Log
brushless upgrade w/TheDave pwm converter

ive decided to start a build log due to interest in upgrading micro quads to brushless in this thread:

http://www.rcgroups.com/forums/showt...1#post22823965

it was originally discussed as a way to add four hobbyking 2 gram brushless motors to the diy quad. but turns out many of the guys who wanted one of these converters were upgrading stock wlt v939, v929, or v949 rtf quads. it may work with walkera ladybird, mqx, udi, syma. or others too but this is not certain because ive yet to examine the signals from these. below is an updated wiring diagram.

this converter is based on the atmel tiny24 family of micros and translates 1500us motor pwm signals from the fc board to a servo/esc type 1-2ms signal to drive brushless motor controllers. default frame rate is 4ms/250hz but can be user selectable from 32ms/30hz to as fast as 2.08ms/480hz. it works similar to a TheSteve converter but has 4 channels and cost a fraction as much.

at this point, not having a full set of escs and motors, ive hooked up 3 servos and 1 brushless motor to a v929 board and they behaved as expected. the servos jitter slightly due to gyro noise which is normal. not a problem with motors because these variations are averaged out. it remains to be seen if the quad will actually fly properly with 4 motors hooked up but i cant see why not (famous last words! lol! ). ill get a chance when the controllers and motors ordered from hk arrive. meanwhile if any of the guys i sent one to try this out please let us know your results.

this worked "out of the box" using a v929 fc with the 20 or so different types of servos and 8 different escs i tested. for those who just cant leave well enough alone it can be reconfigured for different frequencies by way of a simple serial terminal. grounding pa4 (pin 9) on power up puts it in reconfigure mode and bytes are input to pb1 (pin 3) at 115kb. for example hooking this rx line up to a pc usb idle high ttl serial port dongle will allow changing parameters manually with windows hyperterm or any other comm program. normally this is not required but anyway heres a brief description of some settings:

Code:
;bytes in order: 'e','n',ms1,ms2,of1,of2,sc1,sc2,pw1,pw2,pw3,pw4,ms3,ms4,of3,of4,sc3,sc4
;msX hz  hx dec asc
;2.1 480 64 100 'd'
;4.2 240 74 116 't' default
;8.3 120 63  99 'c'
;2.1 480 65 101 'e'
;2.1 480 54  84 'T'
;4.2 240 4c  76 'L'
;8.3 120 44  68 'D'
;16   60 64 100 'd'
;32   30 43  67 'C'
values are stored in eeprom so they are retained even after power off. i think most applications such as micro quad conversions will work fine with default 4ms (250hz) but in some cases like maybe high performance full size multicopters the period can be sped up to as fast as 2.08ms (480hz). this should be more than enough for the most demanding fc setups. i tested it with a scope but none of my servos worked reliably at that rate. so imo better not change anything and leave the defaults where all my servos and controllers worked. at least for starters.

WARNING: dont use heavy wire on that chip. as i found out some time ago and installerblizz more recently it can cause pins to break off due to leverage effect of heavy stiff wire. thin stranded wire is best for that reason: very flexible and will not stress the pin. i use #36 stranded wire for all these types of projects. its similar to what you see on micro heli tail motors and just perfect for this. also note that coating with a little 5min epoxy will ruggedize the finished module. in fact so tuff you can usually step on it with no damage. make sure its working before you encapsulate though.

thanks to dedmonwakin heres a source of #36 stranded wire:
http://stores.ebay.com/AutoMotion/_i...&_sid=31556971

or lower cost #32 includes 3 colors (toss the plugs):
http://www.hobbyking.com/hobbyking/s...idProduct=9704

below are some photos of a converter wired up for use with v929/v939 fc board. notice im using 3 pin 1.25mm connectors for the escs and 2 pin for the fc board. im also using the same 2 pin male and female for battery connection which allows pass through power to the v939 board. it worked fine for my low current very efficient ap02 and ap03 brushless motors but this method of wiring and these connectors may not be adequate for higher current setups. it might require a "star" configuration and heavier power connectors. ill know more when the matched escs and cheapo 2g motors arrive from hobbyking.
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Last edited by dave1993; Oct 22, 2012 at 04:45 PM. Reason: updated configuration parameter table
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Old Oct 06, 2012, 06:10 AM
RC beginner
New York
Joined Oct 2008
6,054 Posts
i forgot to mention that i have been supplying pwm converter chips to "beta testers' and although theyve all been sent out i will try to get more. let me know in this thread if youre interested.
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Old Oct 06, 2012, 08:33 AM
Tri-Quad-Hexa-Octo-copters!!
United States, TX, San Antonio
Joined Feb 2007
14,588 Posts
Hi Dave,
Most multicopter flight controllers output a normal 1000s to 2000s +/-100s PWM output or so on each end to the ESCs. Some flight controllers like the XAirCraft use 200s to 1200s, or the FY controllers which use ~900s to 1800s. Are your converters adjustable for these PWM range differences? http://www.rcgroups.com/forums/showp...&postcount=946

How are these values user selectable on your converter? I am interested in how to set these up for the fastest input and output PWM rate. You mention ~400Hz and that would be good for multicopter use.
Thanks and Cheers,
Jim
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Old Oct 06, 2012, 08:34 AM
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Dave,
You said ... 1500us to 1-2ms. Maybe 150us to 1-2ms?1500us=1.5ms.In the previous thread you mentioned that V929/V939 provide 120us.Maybe max input is 1500us?
How are the frequencies user selectable?Some program?
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Last edited by midelic; Oct 06, 2012 at 09:08 AM.
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Old Oct 09, 2012, 08:03 AM
RC beginner
New York
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Quote:
Originally Posted by midelic View Post
Dave,
You said ... 1500us to 1-2ms. Maybe 150us to 1-2ms?1500us=1.5ms.In the previous thread you mentioned that V929/V939 provide 120us.Maybe max input is 1500us?
i dont think i mentioned 120us as a pwm input because the converter dont work at that fast a frequency. in any case the v929/v939 varies from about 150us to a maximum of 1500us.
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Old Oct 09, 2012, 03:53 PM
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New York
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Quote:
Originally Posted by jesolins View Post
Hi Dave,
Most multicopter flight controllers output a normal 1000s to 2000s +/-100s PWM output or so on each end to the ESCs. Some flight controllers like the XAirCraft use 200s to 1200s, or the FY controllers which use ~900s to 1800s. Are your converters adjustable for these PWM range differences?
i know the frame rate as weve discussed previously is adjustable because i was able to change that by playing around with ms (millisecond) parameters. 2ms up to 32ms rates were confirmed. afaik nobody has ever done this before unless one of the customers of the guy i did it for tried. so it was nice to know it actually works.

the code was also designed to allow timing changes to the pulse width itself but this has not been verified yet. theoretcally it should be possible by altering the scale (scX) and offset (ofX) variables. theres also variables for the input too (pwX) but again nobody has actually tried it. i vaguely remember some brief testing a year or so back but it wasnt high on the list of priorities because the target app had fixed timing. this time around i was busy enough trying to find viable combinations for frame rate out of the thousands possible so didnt quite get around to it. after all, what do you expect? i only WROTE the program. lol!

Quote:
Originally Posted by jesolins View Post
How are these values user selectable on your converter?
ive added more details in post #1 regarding reconfguration of the converter. so to answer midelics question too, it does not require a special program. any serial terminal can be used. i had good luck making changes with a pc and also with a palmtop computer on the long trip home saturday. in fact it should be possible to use one of the popular iphone or android type pda/cellphones with the right apps. as mentioned it probably aint necessary to play around with this stuff anyway because the default operation should work with our application.

more time will be spent experimenting with this when i get access to my scope again. meanwhile ill be looking forward to hearing about actual quad setups from those who do have enough escs and brushless motors of the same type. the ones i have on the way from hk probably wont arrive for several weeks.
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Old Oct 15, 2012, 01:55 AM
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Do you sell those pwm converter chips??? Considering to get a v929... in the future planning to stuck brushless motors on to them....feasible? seems nice...


edited: unwanted sentences...
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Last edited by ivanwong1989; Oct 15, 2012 at 04:44 AM.
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Old Oct 15, 2012, 04:10 AM
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Quote:
Originally Posted by ivanwong1989 View Post
Do you sell those pwm converter chips??? Considering to get a v929... in the future planning to stuck brushless motors on to them....feasible? I'm on a tight budget.. still a student.
Just a tip: Go step by step and get a v929 first.
Maybe sounding a bit rude, but please giveup repeating "I'm on a tight budget.. still a student" in your posts. Thanks.
The quad clones are really cheap. No need to ask for "gifts" ;-)
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Old Oct 15, 2012, 04:35 AM
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lol.... just planning ahead..... haha. See further wouldn't be a bad thing would it?
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Old Oct 15, 2012, 11:31 AM
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Dave - I have not received my converter chip yet.
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Old Oct 15, 2012, 11:51 AM
RC beginner
New York
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they were supposed to go out previous saturday but i suspect due to holiday not til tues. give it a couple more days then let me know either way.

i got a few guys requesting more details on physical wiring methods. i used 1.2mm 3pin parkzone type servo/esc connectors and they still end up bigger than the converter itself. only other approach is direct wiring but i like to stay modular, at least for starters. ill take some pics of my test setup and put them up when i get a chance.
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Old Oct 17, 2012, 02:27 PM
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It came in the mail yesterday. Thanks! I had no idea how tiny it was! I'm very near sighted so I'll definitely be taking out my contact lens to solder this guy up. I've got some scrap PC parallel cable that I am going to use. The spacing between each conductor is tight and their all being attached together should make it pretty secure. I'll try to remember to throw up a pic tonight. The pins are so short I don't see any other option than direct soldering.
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Old Oct 17, 2012, 08:23 PM
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Well, I got it all soldered up but then one of the pins broke off right at the chip. It is ruined. I didn't bend it back and forth either - it just came off. I'm done with this. My lovely fiance is giving me a transmitter and receiver for my birthday in a few weeks, and with my esc's and motors almost here I'm just going to buy a HK flight controller and be done with it. I'd like to add that I have been soldering since I was 8 years old and even magnified these little pins require some serious skill - the whole chip is HALF the diameter of a penny! This is not for most hobbyists. Good luck to anyone else attempting this build. I'm out. Peace.
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Old Oct 18, 2012, 06:38 AM
Tri-Quad-Hexa-Octo-copters!!
United States, TX, San Antonio
Joined Feb 2007
14,588 Posts
My converters just arrived too. Micro-surgery time for sure. Did you use wire wrap wire Dave?
EDIT: Per Dave do not use this old photo of his to build your converter. Use his schematic in post #1!


On your diagram, you are using pin5 and not pin 9.(EDIT: or is it pin 10 and 6 since you are showing the top view and the photo is the bottom view?) Did you change the pins in code after the photo above was taken?

Also on your diagram I would not recommend ganging all ESC 5v power lines together. See the ESC section TIP 8 in the Quadrocopter and Tricopter Info Mega Link Index

Cheers,
Jim
Quadrocopter and Tricopter Info Mega Link Index
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Last edited by jesolins; Oct 18, 2012 at 05:49 PM.
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Old Oct 18, 2012, 07:31 AM
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The schematic shows top view with the pin out pointing down.
If the pins are bent upwards against their normal position( pointing down) this can cause pin breakage easily.It happened to me many times.Bending pins at the bottom is recommended.
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Last edited by midelic; Oct 19, 2012 at 02:29 PM.
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