RC throttle interface build tutorial........

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recumpence   100 GW

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Re: RC throttle interface build tutorial........

Post by recumpence » Sep 16 2010 2:51pm

The POT resistance does not matter, ironically.

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Kepler   1 GW

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Re: RC throttle interface build tutorial........

Post by Kepler » Sep 16 2010 6:01pm

I have built this servo tester a few times. Its about as simple as it gets. Very easy to build and you get the parts from your local electronics supplier for a few dollars. Still easier to use to convert an existing but is a viable alternative.
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Re: RC throttle interface build tutorial........

Post by Miles » Sep 16 2010 6:09pm

Wrong file uploaded, I think :wink: Either that or a coincidence of file names.......


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Re: RC throttle interface build tutorial........

Post by Hillhater » Sep 16 2010 8:46pm

spinningmagnets wrote:
2) insert a jumper lead from the input signal pin to the potentiometer socket centre pin location.
Hillhater, could you please post a pic of this, perhaps add a red arrow?...
...
Ooops ! .. sorry did a green arrow instead of red ! :lol:
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Re: RC throttle interface build tutorial........

Post by bandaro » Sep 16 2010 8:49pm

so any idea on the hall effect throttle replacing the pot throttle? will it work?

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Re: RC throttle interface build tutorial........

Post by Hillhater » Sep 16 2010 9:25pm

bandaro wrote:so any idea on the hall effect throttle replacing the pot throttle? will it work?
I am using a Hall throttle with the turnigy set up described previously. No problems.
. .well actually i am still having a lot of issues with "sync failure" under load, ...but that is nothing to do with the throttle.
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Re: RC throttle interface build tutorial........

Post by jag » Sep 16 2010 9:42pm

Hillhater wrote:
bandaro wrote:so any idea on the hall effect throttle replacing the pot throttle? will it work?
I am using a Hall throttle with the turnigy set up described previously. No problems.
. .well actually i am still having a lot of issues with "sync failure" under load, ...but that is nothing to do with the throttle.
The ability to use a hall throttle is good news. No potentiometer track to wear out, and quality hall throttles seem cheaper than quality pot throttles.

Are there any issues with the different characteristics for halls? ie the throttle response curve seem wierd? or is missing top and bottom part?

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Re: RC throttle interface build tutorial........

Post by Kepler » Sep 17 2010 12:06am

Miles wrote:Wrong file uploaded, I think :wink: Either that or a coincidence of file names.......
Opps. :oops: I'm a duffa. All fixed :D
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Re: RC throttle interface build tutorial........

Post by Kepler » Sep 17 2010 12:29am

Hillhater wrote:
bandaro wrote:so any idea on the hall effect throttle replacing the pot throttle? will it work?
I am using a Hall throttle with the turnigy set up described previously. No problems.
. .well actually i am still having a lot of issues with "sync failure" under load, ...but that is nothing to do with the throttle.

Hold the phone!!!

You are using a Hall effect throttle where a 5K was used just by putting in a jumper? You have gone from a resistive change to a voltage change. This needs more explanation on how this works.

You didnt tell us this when you were talking about sync issues. I wonder if your setup has lost resolution and pulse width is increasing too quickly at the lower end of your throttle range now.

The prototype interface I am involved with at the moment can run a Hall or a 5K throttle but needs a different range set to provide the correct output when changing from one to another. Subsequently it needs a processor and software to do this.

Has anyone else modified a servo tester to take a hall throttle or have I just not been paying enough attention. Lets face it, who want to spend $50 bucks on a magura, when you can buy a Hall throttle for $12
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Re: RC throttle interface build tutorial........

Post by Hillhater » Sep 17 2010 1:04am

Kepler wrote:
You are using a Hall effect throttle where a 5K was used just by putting in a jumper? You have gone from a resistive change to a voltage change. This needs more explanation on how this works..
Sorry Kep' im no sparky just a "suck it and see" idiot with a hot soldering iron ! :)
The shop that sold me the throttles said they were Hall effect so i simply hooked up the wiring ,black to -ve, red to +ve and white to "S" inputs on the servo tester and then "jumped the "S" input pin to the mid socket of the pot location.
( note, on the Turnigy Servo tester inputs, +ve and -ve both link direct to the other pot sockets, and the "S" pin is not connected to the board circuits)
The end result seems to work fine , but i will check with a tach' to be sure i am not missing any range.
Kepler wrote:You didnt tell us this when you were talking about sync issues. I wonder if your setup has lost resolution and pulse width is increasing too quickly at the lower end of your throttle range now.
Unfortunately, the "sync " issues were there before i wired up the throttle...just using the servo tester "au naturale" , and they persist unchanged after install. :cry:
I have to peddle up to about 20kph before powering up the drive, to have any chance of avoiding "sync failure" :cry:
I guess i am going to have to try another motor...or ESC !! :x
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Re: RC throttle interface build tutorial........

Post by Miles » Sep 17 2010 1:22am

AussieJester wrote:And a glimpse of what Kepler has planned next maybe :-P
That's a Hal production :wink:

http://endless-sphere.com/forums/viewto ... 08#p130908

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Re: RC throttle interface build tutorial........

Post by bandaro » Sep 17 2010 2:52am

waaaiiiiittttt.....


hillhater, yours is done different from the one first posted up right? you put the jumper in and then connected the throttle to the "in" side and your esc has a bec inbuild so you used that to power the tester right? with the power coming through the tester backwards (starting at the "out" side)?

i got the turnigy tester sitting in front of me and it appears that signal wire on the "in" side is not connected to anything, so if the above is not right then im well and truly confudled. you just did this for building simplicity?

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Re: RC throttle interface build tutorial........

Post by Hillhater » Sep 17 2010 5:45am

When you run the ESC ( with BEC) with just a servo tester you simply plug the ESC into the "output" side of the ST... then use the ST as the throttle.
So you dont need the power feed to the "input" side of the ST.
when you remove the pot from the ST, and trace the circuit you will see how the +ve and -ve input pins are fed to the two outer pot connections, so using them to link to the throttle was logical ( to my tiny mind at least).
Then as you say, seeing the S input pin was not actually connected, i simply "jumpered" it to the centre pot connection on the board.
This gives me a "plug in" throttle connection.
As you say i did this for simplicity ( and in total ignorance of if it would work !) but it seem to function perfectly.....so far ! :o
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Re: RC throttle interface build tutorial........

Post by bandaro » Sep 17 2010 6:22am

awesome, then thats good enough for me, i can see anything wrong with it apart from the basic possible problem of hall vs pot.

does someone who understands all this electrical component stuff see a reason why the hall cant simply replace a pot? as it stands i think ill just solder up an identical circuit as hillhater, and cross my fingers, lift the rear wheel off the ground and make sure the wheel speed it right to test full throttle rpm.

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Re: RC throttle interface build tutorial........

Post by Hillhater » Sep 18 2010 3:59am

Well i checked the motor max speed at no load = 4780 rpm on 18.5 V which is on par for a 250KV motor.
Throttle range from 0 - max seems ok too.
Also did a quick check on the throttle to be sure it is Hall effect... no detectable resistance change on Mmeter when operated.
I will try to do a voltage (0-5v ?) check on it also ....when i figure out a suitable volt supply. :wink:

A further thought on this Hall throttle issue..
..this Turnigy servo tester has a "Auto" function (firmware ?) that will automatically run the ESC through the full speed range .. bypassing the potentiometer.
that would suggest that there is something else, other than the 0-5k pot, "on board" to control the output.
Maybe the Hall throttle is somehow using that firmware system ?? ( just random thoughts :? )

Still puzzling the Sync failure problem though ?..
I think most of you (Kepler, & todd) are using external BEC's or even separate battery supply ? so i am wondering if the integral BEC i an using could be a part of the problem
.. I think i will try an external 5v power supply instead of using the BEC from the ESC.
... just wondering if it may change things with a "clean" or independent 5v supply. ? ... but i will have to isolate the BEC somehow ?
Any thoughts ?

Hey,..Bandero.... is that soldering iron hot yet ? :)
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Re: RC throttle interface build tutorial........

Post by bandaro » Sep 18 2010 4:24am

not just yet, waiting on postage for parts to heat up but i can assure you it will take up smoking within minutes...

if it works for your esc then its good enough for me. if it fails on me ill just chuck the pot in the throttle or make a thumb one, idk... ill be creative. thanks for the help guys, ill link the stuff i used if it works coz i got a much cheaper throttle than the magura.

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Re: RC throttle interface build tutorial........

Post by Kepler » Sep 18 2010 5:18am

Hillhater,

I normally use the onboard BEC. I am sure an onboard or external will make no difference.

You did mention you motor screams at high RPM. Normally they are quite quiet. I wonder if you have a bad motor.
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Re: RC throttle interface build tutorial........

Post by Jeremy Harris » Sep 18 2010 6:12am

Hillhater wrote: A further thought on this Hall throttle issue..
..this Turnigy servo tester has a "Auto" function (firmware ?) that will automatically run the ESC through the full speed range .. bypassing the potentiometer.
that would suggest that there is something else, other than the 0-5k pot, "on board" to control the output.
Maybe the Hall throttle is somehow using that firmware system ?? ( just random thoughts :? )
All the servo testers that I've seen recently have used a small microcontroller to generate the PPM signal for the servo. They often have two switchable options, one that uses the pot to control the waveform and one where the microcontroller just cycles through the allowable range.

The pot connections vary from one type of servo tester to another. I have one here that just uses two connections from the pot so is effectively just reading resistance - this wouldn't mate up with a Hall throttle well. I have an older one here (from my local model shop, with no brand name) that uses a 10K pot wired to give a 0 to +5V signal to the microcontroller. This may work with a Hall throttle, but the throttle range would probably be wrong, as the Hall throttles usually have about a 1.5 to 3.5V output voltage range when run from a 5V supply.

It's pretty easy to make an interface that will run from the 5V BEC supply and allow a Hall throttle to be used. A simple microcontroller, like the 8 pin Picaxe 08M, will run on +5V, draw negligible current, accept any analogue voltage input in the 0 to 5V range and output a PPM waveform that will directly drive an ESC. All that's needed is a bit of simple code (written in a form of BASIC) that will read the voltage from the throttle and use this to set the PPM signal. This is pretty easy stuff even for someone with no experience of writing code. The pseudo code would look something like this:

Mainloop:
Read ADC ; this read the voltage from the Hall throttle and converts it to a value between 0 and 1023
Subtract zero offset number ;the throttle isn't at 0V when closed, so the offset needs to be subtracted
Multiply or Divide by a factor to get the right SERVOPOS value ; this changes the raw voltage reading to a throttle value
Send throttle value number to SERVOPOS ; this tells a pin on the controller to generate a servo PPM pulse train
GOTO Mainloop ; this just loops the programme back to do the above sequence as fast as possible.

I've already done a board layout for a multipurpose throttle interface, using this controller (http://endless-sphere.com/forums/viewto ... 05#p310462 ). The board is 1" square and just as three throttle wires going in and three wires going out to the ESC (assuming the ESC can provide +5V). The board also has a serial programming port so that the code can be loaded from the free Picaxe programming utility to the chip. To be honest there's no need for a circuit board for something this simple, you could just as easily stick the chip on a small bit of perf board to make the necessary connections, maybe potting the thing in a blob of resin or hot melt glue to make it watertight.

I've not got the time to make these things as a production article, but I may be able to sort the code out, test it and publish it so anyone else could make one fairly easily.

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Re: RC throttle interface build tutorial........

Post by spinningmagnets » Sep 18 2010 11:20am

Jeremy, its good to have several throttle options, and you are making a very persuasive case for the method you describe. If you write the code, build a prototype, and test it for function,...There are several posters (me included) who would be glad to produce a pile of them. I can't speak "electronic-ese" but I am very good at following directions (especially with included pics), and I am a fast learner.

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Re: RC throttle interface build tutorial........

Post by Hillhater » Sep 18 2010 8:50pm

Jeremy Harris wrote: It's pretty easy to make an interface that will run from the 5V BEC supply and allow a Hall throttle to be used. ....
Jeremy, I am sure many of you electrical guys can do this easily , but unless i am being delusional,...it seems that this can be done using the $5 Turnigy Servo tester and one simple jumper wire mod....even more easily ! ?
I would ask that someone else repeat this to verify it before we mislead too many people.
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Re: RC throttle interface build tutorial........

Post by Jeremy Harris » Sep 19 2010 3:17am

Hillhater wrote:
Jeremy Harris wrote: It's pretty easy to make an interface that will run from the 5V BEC supply and allow a Hall throttle to be used. ....
Jeremy, I am sure many of you electrical guys can do this easily , but unless i am being delusional,...it seems that this can be done using the $5 Turnigy Servo tester and one simple jumper wire mod....even more easily ! ?
I would ask that someone else repeat this to verify it before we mislead too many people.
Maybe.......... The servo testers I've looked at have varied a fair bit in terms of how they are driven, some accept a 0 - 5V input from a pot wired across the supply, some accept a variable resistance input and some have padding resistors either side of a pot to reduce the effective voltage output range into the microcontroller. A Hall throttle gives an approximate 1V to 4V output, or thereabouts. Maybe this voltage range works OK with a few servo testers, but it isn't really a universal solution as servo testers seem to vary a fair bit, based on the few I've looked at. It may even be something that only works on a few of the same type of servo tester, due to manufacturing tolerances.

If Turnigy keep their circuit the same (a big ask for a bit of random Chinese kit that's probably made by one of a few dozen suppliers of the same part to Turnigy) then your solution may be the simple answer. I suspect that what works well on one tester might not work on another bought a few weeks later though.

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Re: RC throttle interface build tutorial........

Post by Jeremy Harris » Sep 20 2010 6:52am

OK, I've had a go at making a simple Picaxe interface this morning. All told it took about an hour, including time spent writing the short bit of code. Here's a quick description of what I did.

First off, I wired up a Picaxe 08M microcontroller (see here for one source of these http://www.rev-ed.co.uk/picaxe/) so that the +5v pin (pin 1) was connected to the Hall throttle +5V, the 0V pin (pin 8) was connected to the Hall throttle 0V and the Hall throttle output was connected to the Picaxe 08M analogue input 1 (pin 5). The three leads to the ESC were connected to the +5V and 0V pins, with the PPM wire from the ESC (normally white or orange) connected to digital output 2 (pin 4) on the Picaxe 08M. A small capacitor of 0.1uf was connected across the Picaxe power pins.

The Picaxe 08M was plugged in to a programming breadboard and hooked up to the PC using a serial/USB lead. The following simple code was loaded into the chip:

init:
servo 2,75 ;initialises servo timer and sets PPM to 0.75mS (zero throttle)
main:
symbol throttle_input = w0
symbol throttle_output =w1
symbol ppm_output =w2
loop1:
readadc10 1,throttle_input ;Read Analogue voltage from Hall throttle at 10 bit resolution and store in throttle_input
throttle_output = throttle_input - 197 ;Subtract zero offset value of 197 from Hall throttle reading to correct for Hall throttle voltage being non-zero when throttle closed
ppm_output = throttle_output * 36 ;these three lines convert throttle value to ppm range of 0.75mS to 2.25mS
ppm_output = ppm_output / 130
ppm_output = ppm_output + 75 ;Add zero offset of 0.75mS to ppm range to get true ESC zero throttle point
servopos 2,ppm_output ;send pulse width to ESC ppm signal

goto loop1

This works fine, with a very fast throttle response. The circuit I knocked up is a lash-up and the code uses an extra variable that's not needed, but this could very easily be turned into something that's quite versatile at processing throttle signals and adding various features. This baby 8 pin microcontroller will typically hold around 80 lines of code, so the little bit of code above is only using a small proportion of its capabilities.

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Re: RC throttle interface build tutorial........

Post by spinningmagnets » Sep 20 2010 2:51pm

Wow! Thanks Jeremy, I appreciate your being so helpful with your experience and knowlege.

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Re: RC throttle interface build tutorial........

Post by Hillhater » Sep 20 2010 7:59pm

Jeremy Harris wrote:OK, I've had a go at making a simple Picaxe interface this morning.
...... Here's a quick description of what I did.
Jeremy
Your knowledge and abilities exceed even my capacity to understand WTF you are saying !!! :shock: :lol: :lol: :wink: )

.... but it sure sounds like a good idea !
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