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

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

Postby Hillhater » Sat Sep 18, 2010 8:50 pm

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........

Postby Jeremy Harris » Sun Sep 19, 2010 3:17 am

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.

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

Postby Jeremy Harris » Mon Sep 20, 2010 6:52 am

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.

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

Postby spinningmagnets » Mon Sep 20, 2010 2:51 pm

Wow! Thanks Jeremy, I appreciate your being so helpful with your experience and knowlege.
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Re: RC throttle interface build tutorial........

Postby Hillhater » Mon Sep 20, 2010 7:59 pm

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

Postby AussieJester » Mon Sep 20, 2010 8:06 pm

Hillhater wrote:
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 !



ROFL...don't worry...Jeremy's words and actions have that effect on alot of people, in fact hahaa, I should probably
be the president of the 'WTF is Jeremy Saying' club :mrgreen:

Keep up the good work Jeremy....i think, your not making weapons of mass destruction are you? :shock: :mrgreen:
You remind me of this chap you have something else in common
too, he was also on a episode of Scrap Heap Challenge, he helped one of the teams build a pulse jet.

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

Postby Jeremy Harris » Tue Sep 21, 2010 1:29 am

Thanks for the kind words and sorry for the furrowing of brows I've caused................

In essence, all this chip is doing is reading the value of the voltage from the Hall throttle and directly converting it into the right type of pulsed signal to drive an ESC. It helps not to think about the chip as a microcontroller, but just think of it as a very versatile electronic building block that can convert signals from one form to another, in pretty much any way you want, just by changing a few lines of code, rather than by changing components.

BTW, I know Bruce. As well as being a fellow Scrapheap expert, he's also done some pretty remarkable stuff with pulse jets. I managed to scare the **it out of some folks where I used to work when I showed the anti-terrorist team his 'Build a cruise missile for less than $5000' site a few years ago. Even better are some of his other pulse jet projects, like the pulse jet powered go kart. I bet his neighbours love him as much as the CIA and NZ government (anyone who's heard a pulse jet run will know what I mean.........).

There must be something about Kiwis that makes them even more eccentric than us Brits, this guy: http://www.asciimation.co.nz/ for example, is another Kiwi with way too much time on his hands and some truly brilliant projects (check out the turbojet-powered beer cooler...........).

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

Postby AussieJester » Tue Sep 21, 2010 1:41 am

^^LOL i spotted the jet beer cooler few years back
such a complete waste of money and time...i so want it hahaha

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

Postby full-throttle » Wed Oct 06, 2010 8:09 pm

Looks good Jeremy,

I would right-shift by 7 (essentially divide by 128) instead of
Code: Select all
ppm_output = ppm_output / 130
ie
Code: Select all
ppm_output = ppm_output >> 7
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Re: RC throttle interface build tutorial........

Postby Jeremy Harris » Thu Oct 07, 2010 2:15 am

full-throttle wrote:Looks good Jeremy,

I would right-shift by 7 (essentially divide by 128) instead of
Code: Select all
ppm_output = ppm_output / 130
ie
Code: Select all
ppm_output = ppm_output >> 7


Shift right isn't a valid operator on the 08M Picaxe, plus the divisor needs to be 130 to get the correct value of pulse width.

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

Postby full-throttle » Thu Oct 07, 2010 11:04 pm

You right - had a quick look at the instruction set, my bad.
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Re: RC throttle interface build tutorial........

Postby bandaro » Thu Oct 14, 2010 11:49 pm

ok, got my throttle up and running, and i can confirm that for the electrics i got it works. i used the same jumper method in the picture a page or so ago on a turnigy servo tester, and the cheapest hall effect throttle i could find.

throttle i got (10 bucks posted on ebay):
http://cgi.ebay.com/ebaymotors/Razor-El ... 4496wt_939


servo tester (the turnigy one for 6 bucks, jeremy said they may change the electrics, but the ones they were supplying a month ago work):
http://www.hobbycity.com/hobbycity/stor ... oduct=8296

am yet to test the final rpm (need a few more parts as i only have the cycle computer to measure speed, then deduce rpm) but the esc has a little led in it that lights up at about 90% of the twist, so i am taking it this led means that the esc is full throttle. otherwise it seems smooth and consistent with the more twist it gets.

total cost for parts shipped to your door would be less than $20, then you will need a 4-6v power source (ubec) for the servo tester, as you would if using the magura throttle. for any interested i am just using the cheapie k-force 120 esc for now, see how it holds up for my first build.
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Re: RC throttle interface build tutorial........

Postby Hillhater » Fri Oct 15, 2010 12:38 am

Bandaro,
just a tip ...
on the Turnigy servo tester, i "clipped" off the top of the "mode" button (so that it is below the surface of the enclosure),to prevent accidentally engaging "Auto" mode when you are running ! :shock:
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Re: RC throttle interface build tutorial........

Postby bandaro » Fri Oct 15, 2010 1:39 am

lol, good to see your on the ball hillhater, but dw, i already trimmed that button off and taped the whole thing up ready to shove into a box :D
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Re: RC throttle interface build tutorial........

Postby Hardcarve1 » Fri Oct 15, 2010 2:50 pm

If I want to use the turnigy ST on a CC 110 HV using a hall thumb throttle I will need to use a BEC. How would we wire the BEC into the servo tester? would it be similar to how Matt has done his?
I got lost in what Jeremy was saying which I think was about this. If anyone could do give some explanation as I have ordred the turnigy and would like to have a go at wiring it up.

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

Postby bandaro » Sat Oct 16, 2010 2:15 am

for mine i simply plugged the bec into one of the 3 servo places, right under where the esc went in.

means the power is being put in "reverse" direction but it is all the same.
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Re: RC throttle interface build tutorial........

Postby Hardcarve1 » Sat Oct 16, 2010 4:56 am

I see it now, I thought their was just one input & output but I can see the multiple plug points.
Thanks
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Re: RC throttle interface build tutorial........

Postby Wheazel » Fri Dec 03, 2010 11:16 am

This thread is full of awesomeness. Thanks for the tutorial.
Input regarding availability in Europe is appreciated. Only seem to find american sites selling the throttle.
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Re: RC throttle interface build tutorial........

Postby Brushlessboy16 » Fri Dec 03, 2010 9:38 pm

Depending on your input voltage

This unit is good for 10s Lipo input
http://www.hobbyking.com/hobbyking/stor ... duct=10313
Very cheap site and they have many warehouses around the globe :)
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Re: RC throttle interface build tutorial........

Postby recumpence » Sun Dec 05, 2010 2:36 pm

Hey Guys,

I wanted to post a quick update..........

I spent the morning building a bunch of throttle interfaces. All pending orders are filled and I have two throttles finished in stock. :)

Sorry for the delay. I had an issue with regulators and a couple other minor details. I am up to speed again, however. :)

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

Postby deVries » Sun Dec 05, 2010 4:44 pm

bandaro wrote:ok, got my throttle up and running, and i can confirm that for the electrics i got it works. i used the same jumper method in the picture a page or so ago on a turnigy servo tester, and the cheapest hall effect throttle i could find.

am yet to test the final rpm (need a few more parts as i only have the cycle computer to measure speed, then deduce rpm) but the esc has a little led in it that lights up at about 90% of the twist, so i am taking it this led means that the esc is full throttle. otherwise it seems smooth and consistent with the more twist it gets.

for any interested i am just using the cheapie k-force 120 esc for now, see how it holds up for my first build.

Hi Bandaro, just thought I'd check-in to see how the rpm range worked with this setup? You got full range & good control w/throttle you bought? Also, how is that 120 k-force ESC working? Did you add extra caps or mod it?

Thanks! :mrgreen:
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Re: RC throttle interface build tutorial........

Postby HumboldtRc » Sun Dec 05, 2010 10:41 pm

recumpence wrote:Hey Guys,

I wanted to post a quick update..........

I spent the morning building a bunch of throttle interfaces. All pending orders are filled and I have two throttles finished in stock. :)

Sorry for the delay. I had an issue with regulators and a couple other minor details. I am up to speed again, however. :)

Matt


What all do your throttles consist of? What features do they have?

I just finished mine, with a 0-5k sliding pot (in a custom cable throttle box) to a Turnigy servo tester to a servo speed regulator then to the esc's.
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Re: RC throttle interface build tutorial........

Postby Hillhater » Sun Dec 05, 2010 11:42 pm

HumboldtRc wrote:
I just finished mine, with a 0-5k sliding pot (in a custom cable throttle box) to a Turnigy servo tester to a servo speed regulator then to the esc's.


what does the .."servo speed regulator" ... do for you ??
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Re: RC throttle interface build tutorial........

Postby recumpence » Mon Dec 06, 2010 8:19 am

HumboldtRc wrote:
recumpence wrote:Hey Guys,

I wanted to post a quick update..........

I spent the morning building a bunch of throttle interfaces. All pending orders are filled and I have two throttles finished in stock. :)

Sorry for the delay. I had an issue with regulators and a couple other minor details. I am up to speed again, however. :)

Matt


What all do your throttles consist of? What features do they have?

I just finished mine, with a 0-5k sliding pot (in a custom cable throttle box) to a Turnigy servo tester to a servo speed regulator then to the esc's.


It is a simple PWM board with 5v regulator to power it in a water resistant heat shrinked package with a Magura twist grip throttle. :)

It is a tried and tested design. All units are hand built and bench tested before shipping.

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

Postby LI-ghtcycle » Fri Dec 10, 2010 1:27 pm

Wow, good stuff in this thread!

I wanted to get some advice on two parts however.

1) I had some real trouble removing the Servo Tester POT even with my 60W iron (I tired it first with my 30W to avoid getting things too hot) and I am still not 100% sure that I didn't damage the PCB in the process, I have been considering getting a "vacuum bulb" designed to suck away the solder, but for now I have been using the heat and tap method, and also tried by heating all three leads at once on the POT, but I REALLY struggled to get it loose even when I had all the leads just sitting on the PCB. Is there something I am missing? I have to work in a pretty cold (about 55 DEG F) garage, maybe that is part of the problem.

2) I am unclear about weather or not I should be fine using the BEC on my ESC to power the Magura Throttle, or if I will still need to add an extra BEC to power things?

Oh, one more thing, I got to wondering since using the extra POT that I removed from the ST, if I understand correctly using it as a "throttle limiter" restricts total voltage, and say if I wanted to run 8S and regulate down the speed, that although it wouldn't regulate amps, would I not be able to have it regulate the voltage down so that it could at as if I were just running 6S while under higher load (climbing hills) and then turn it back up for a long flat stretch. Am I correct in my understanding?

Thanks! :)
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http://www.endless-sphere.com/forums/viewtopic.php?f=3&t=29810&p=475990#p475990
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