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Author Topic: OK so what am i doing wrong???  (Read 15388 times)

Stavros

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Re: OK so what am i doing wrong???
« Reply #50 on: August 19, 2008, 10:43:06 PM »

Whiskey frank just go out and buy a Mtronics 40 amp speed controller it will handle the power of your Graupener 700bb turbos


Stavros
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whiskeyfrank

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Re: OK so what am i doing wrong???
« Reply #51 on: August 19, 2008, 10:56:44 PM »

Thanks for all your help, im going to get a new esc and see what happens.

By the way took the esc back to the model shop and they told me to "go away" but no so nicely, so thats good service, NOT, feel like naming and shaming.

Maybe ill get it working eventually and arrive on lake Llanberis one day!!!!

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Stavros

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Re: OK so what am i doing wrong???
« Reply #52 on: August 19, 2008, 11:18:30 PM »

Where you from come on name and shame the model shop


Stavros
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wombat

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Re: OK so what am i doing wrong???
« Reply #53 on: August 19, 2008, 11:37:23 PM »

WhiskeyFrank

Can't see anything wrong with the setup you showed in the photo - so without getting probes onto the circuit, all I can suggest is that the ESC is playing games. One possibility is that it cannot cope with the inrush of the motor. Seen this with one ESC - edge the throttle up slowly and it ran fine, bang it onto full and the current surge trying to make the motor spin causes the ESC to trip. Were there any instructions with it?

PMK/Bluebird

Looking at the booster circuit - I suspect it will shift the neutrals - the rise and fall times will be fairly leisurely - this will effectively change the pulse width  - especially if (as I suspect) the rise and fall times are different. It will pull down easier than it pulls up so will tend to narrow the effective pulse width. YOu might get some improvement if you reduce the resistor values a factor of 10 or possible 100.

I hate to suggest it, but has anyone tried a simple pull-up resistor - say 1K ?

Pulse width is the information carrier so it doesn't surprise me the frame rates differ for different sets. Depends on the deadband between pulses and the size of the framing pulse. Again 2.2V doesn't surprise me too much. TTL specs give a minimum voltage for a high output as 2V. CMOS will pull to the rail if it is unloaded but the output will droop with load.  

Wom




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OMK

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Re: OK so what am i doing wrong???
« Reply #54 on: August 20, 2008, 12:37:04 AM »

"I hate to suggest it, but has anyone tried a simple pull-up resistor - say 1K ?"

Hello, Wom.
No - I hadn't thought to stick a pull-up res' there. (You're talking of a pull-up across the output, right?).
I thought it a bit iffy to have those specified resistors less values than shown because, dig this, the original trannys on the breadboard were a couple of Darlingtons I found in the junquebox. Loads of HFE on those, hence........
I found that it worked just the same when I swapped out the trannys for a couple of bog-standards, even with those res' values shown.
One point of interest...
The Rx I used for testing the booster was one of those Futaba FASST jobbies. I'm reading approx' 2.8v on the pulse. The two transistors - as you know - are robbing that extra V from the Rx battery itself, now with enough zip to run the inputs of a '4013 MOS.

Re neutrals:
I can't say I noticed any difference regarding rise/fall times. Leastways, none that I could detect on my battered old 'scope.

You've likely also noticed that, regarding frame rates, it's nigh impossible to tell any difference in servo speed if the rate is, say, 25mS or even 15mS.
Talking of similar........ Some of the fly boys, with their new-fangled 'latency' buzzword would swear that they can tell a difference, but I reckon they're not from this planet.



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barry park

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Re: OK so what am i doing wrong???
« Reply #55 on: August 20, 2008, 03:11:02 AM »

Whisky, I'll swap your esc's for two surplus esc's I have here if you can wait till you get a packet next Wednesday.They've run 700BB turbo motors (PM me with your addy if you want to take me up on it)

Wom, I asked Whisky to use a bulb in case current trip was below 700 stall.....no joy.

PMK,Bluebird
   Wom is spot on but try 2k2 to save a couple of milliamps.
As with all high gain inputs there needs to be an RF block so there is about 1 nF shunted from collector to ground within the esc.
It's the risetime that's too slow,transistor gain makes no difference. PMK's adapter should really put 1nf at input.
 
Thanks PMK for the description of pos neg shift but I see now that you your confusing it with polarity of the servo pulse train.I wasn't sure what you were getting at.
 
On the voltages...the Futaba servo standard has always been TTL (2.2 on 5volt rail with light load) and receivers only increased to 2.5 because Futaba,using new 4000 series CMOS (rail-rail) in their receivers with a low drop 2.5 low drop reg. supply and then through a 270 ohm resistor.Some receivers did put out higher Rail-Rail pulses(Fleet,Acoms,bec) but that was incidental and never a standard.
 That is where Bluebird's ESC designer c****d and up and nearly caved in under the deluge. Only just worked on 5 volt BEC and no more.
It's nowt to do with PCM sets....... it's down to CMOS threshold within the decoder that was assigned as an input pin (minimum 2.5 volt input at 5 supply)
Their first esc's used,an old servo chip, ZN409 could handle TTL levels but when the big changeover happened....oops.

Incidentally the early 10 and 15 amp models had two serious "issues" when operated on anything other than 5 volt BEC. Their ZN409 had an inbuilt voltage dependency to stretch throttle which compensated for low battery in early servos and maintained arm movement speed.
 When used in ESC's ,Futaba,Fleet,Hunter neutralised that tendency,as per the ZN409 data application recommendation. Early ZN409 E********ze and A****n ESC's didn't which meant that when the receiver pack went low the ESC noticeably went full out at only midrange throttle. Throttle setting had to be changed if batteries switched between NI-Cd and alkaline and E********ze could barely reach full throttle with four new alkaline batteries  and the ESC throttle trim maxed out.

 Another "small issue" in the last two types was the FET transistors were not fully switched on at low battery values.Consequently drive transistor resistance crept up and overheated,usually melting the two pole relay until the contacts shorted out the supply battery. :o
Fleet,Hunter designed out that possibility by charge pumping the FET gate voltage and Futaba used bipolar drive.Other manufacturers used low-threshold gate drive FET transistors.

Bluebird confirmed to me.(thanks O0) that ihis esc was yet another voltage design "issue" because I almost half believed the PCM story. If the supply voltage to the ESC is lowered to 5.0 it should work because that lowers the ESC CMOS input to just accept 2.5 volt servo pulses from mini receiver. Same reason why Acoms and Fleet servos will work with Futaba using re chargeargable (1.35 volt ) and not four 1.6 volt alkaline batteries.
Is receiver putting out 2.5 Bluebird? Did I read you had access to a scope?  If receiver pulses are lower the 5.0 bec fix wont work for that Rx.
I initially thought the problem was down to the increased frame rates some PCM users told me. Some PWM receivers grab that reading to enable PCM like error correction. 
DickD,did you read all of that ;) I just skip over long posts.
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barry park

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Re: OK so what am i doing wrong???
« Reply #56 on: August 20, 2008, 07:56:23 AM »

Hi Wombat,

Looking at the booster circuit - I suspect it will shift the neutrals - the rise and fall times will be fairly leisurely - this will effectively change the pulse width  - especially if (as I suspect) the rise and fall times are different. It will pull down easier than it pulls up so will tend to narrow the effective pulse width. You might get some improvement if you reduce the resistor values a factor of 10 or possible 100.
Spot on there.  I said 2.2k to spare 2 mA.
Quote
I hate to suggest it, but has anyone tried a simple pull-up resistor - say 1K ?
A simple "open-collector" type pull up instead of booster will only add a fraction of a volt due to intrinsic diode in the output (shift reg.) chip
Quote
Pulse width is the information carrier so it doesn't surprise me the frame rates differ for different sets. Depends on the deadband between pulses and the size of the framing pulse.  

I agree there. I was offering unsolicited raw data to PMK and Bluebird because some after market designers are taking liberties and assuming a generous frame time......I speculated Bluebird's esc designer could have wrongly assumed a ~20 msec frame and designed in the so called "incompatibility with some PCM receivers" .....logical enough! (IPD PPM receiver"grabs" the frame period to help generate PCM quality failsafe. 8))

Since PCM sets don't have to output each channel sequentially like a PPM set they are not tied to the longer frame periods.
Bluebird's soldering job appears to provide proof the problem was the ESC voltage threshold was too high to recognise receiver "1's".
By the same token ,dropping the ESC voltage to 5 volts should have then allowed the ESC to pick up pulses as they'd just be within CMOS range.
Bluebird tried four flat rechargeables (~5 volt) and it didn't work so I wonder if the ESC input is a schmitt trigger set too high.There's definitely a capacitor on the input which is shortening pulses.

I think I'm adding to the myth that electrics is a black art :embarrassed:....enough said by me.
 
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FullLeatherJacket

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Re: OK so what am i doing wrong???
« Reply #57 on: August 20, 2008, 08:22:31 AM »

...enough said by me.

Shame.............just when it was getting interesting, too.
FLJ
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DickyD

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Re: OK so what am i doing wrong???
« Reply #58 on: August 20, 2008, 09:37:00 AM »

Do I detect a touch of sarcasm there Dave ?
Still now we all know everything about whatever they were on about, whatever it was. :-\
Very educational, they that knows all about it explaining it to those that know all about it in a language that no one else can understand, I think. :-\

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grasshopper

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Re: OK so what am i doing wrong???
« Reply #59 on: August 20, 2008, 10:58:14 AM »

http://en.wikipedia.org/wiki/Jargon


otherwise known as double-dutch or 'it's all chinese to me'
I was impressed though, now I understand why it's in the 'all things Black Art'
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John W E

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Re: OK so what am i doing wrong???
« Reply #60 on: August 20, 2008, 11:02:41 AM »

And all we want to do is sail a model boat.... {-) {-) {-) {-) {-) {-) O0 :angel:
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FullLeatherJacket

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Re: OK so what am i doing wrong???
« Reply #61 on: August 20, 2008, 11:04:49 AM »

Do I detect a touch of sarcasm there Dave ?

Sarcasm? Moi?? Perish the thought, dear boy!   ::)
FLJ
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DickyD

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Re: OK so what am i doing wrong???
« Reply #62 on: August 20, 2008, 11:39:43 AM »

And all we want to do is sail a model boat.... {-) {-) {-) {-) {-) {-) O0 :angel:
You need to put it on a pond for that John.  ::)
Where's that avatar I sent you ?  :-\
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malcolmfrary

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Re: OK so what am i doing wrong???
« Reply #63 on: August 20, 2008, 11:50:24 AM »

When talking of a circuit with two transistors stretching pulse length, unless they are really horrible transistors, there should be nothing noticeable.  The pulse length is in the order of 1.5 thousands of a second - transistor switching time is a few nanoseconds, a factor of about a millionth - the only bits adding a capacitive element tat would extend this are the junctions of the transistors themselves and the stripboard tracks, and they should be totally insignificant in this application.
That said, it is a pity that there is no actual standard laid down for signals between RX and whatever gets plugged into them apart from whatever arises from what the component industry chooses to offer.  This results in the situation that any compatibility between old and new is accidental rather than intentional.  In the quest to cut costs, this often results in some items not working in the "core area" but in the "safety zone".  This is OK as long as the "safety zones" match.
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Martin13

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Re: OK so what am i doing wrong???
« Reply #64 on: August 20, 2008, 11:52:55 AM »


Still now we all know everything about whatever they were on about, whatever it was. :-\
Very educational, they that knows all about it explaining it to those that know all about it in a language that no one else can understand, I think. :-\



Having an Electronics background myself, I also found the discussion interesting to read. But to those being the majority on this forum, its all double-dutch.

I hope Whiskeyfrank takes up PMK's offer of sending his esc to PMK - I'm very interested in the outcome not to mention that a forum member has offered to look at the item for just the cost of postage - Well done PMK O0

Martin doon under - looking on with interest :) :)
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Circlip

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Re: OK so what am i doing wrong???
« Reply #65 on: August 20, 2008, 12:50:52 PM »

Very interesting and enlightening discourse barry park, welcome to  the gang.
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barry park

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Re: OK so what am i doing wrong???
« Reply #66 on: August 20, 2008, 02:30:23 PM »

When talking of a circuit with two transistors stretching pulse length, unless they are really horrible transistors, there should be nothing noticeable.  The pulse length is in the order of 1.5 thousands of a second - transistor switching time is a few nanoseconds, a factor of about a millionth - the only bits adding a capacitive element tat would extend this are the junctions of the transistors themselves and the stripboard tracks, and they should be totally insignificant in this application.
......... and the load it was driving i.e. inside the ESC
Bluenird ,change R4 to a lower value as Wom says.
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DickyD

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Re: OK so what am i doing wrong???
« Reply #67 on: August 20, 2008, 02:42:10 PM »

When talking of a circuit with two transistors stretching pulse length, unless they are really horrible transistors, there should be nothing noticeable.  The pulse length is in the order of 1.5 thousands of a second - transistor switching time is a few nanoseconds, a factor of about a millionth - the only bits adding a capacitive element tat would extend this are the junctions of the transistors themselves and the stripboard tracks, and they should be totally insignificant in this application.
......... and the load it was driving i.e. inside the ESC
Bluenird ,change R4 to a lower value as Wom says.

Calling John "bluenird" aint doing you no favours old chap >>:-(
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OMK

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Re: OK so what am i doing wrong???
« Reply #68 on: August 20, 2008, 05:15:19 PM »

Bluebird,

It wasn't until I took another butcher's at the schematic that I noticed what all the hoo-ha is about.
Wom / barry park are right; I stand corrected.
See where R4 is shown as 47K? Ignore it - it's a typo. I should have a stuck a decimal point between the 4 and the 7 - 4.7K (or 4K7, or 4700 Ohms - not 47,000 Ohms).
Although, it does work with a 47K there, but........ Well, as we all now know, the rest is history.

My error -- sorry.
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John W E

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Re: OK so what am i doing wrong???
« Reply #69 on: August 20, 2008, 05:24:28 PM »

Hi PMK
Whats a point berween friends  {-) {-)
I will Sort that problem later ,by the way thank you for the offer of the p59
FLJ boyo kindly furnished me with one a while ago  O0

aye
john e
BLUEBIRD
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OMK

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Re: OK so what am i doing wrong???
« Reply #70 on: August 20, 2008, 05:35:44 PM »

John,
I remember reading a piece where a NASA engineer had inadvertantly stuck a decimal in the wrong place and ended up sending a rocket into the sea. Just one iddly-diddly decimal point cost him his job - not to mention his reputation.

Welcome to the P59 club!
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whiskeyfrank

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Re: OK so what am i doing wrong???
« Reply #71 on: August 21, 2008, 08:22:38 PM »

ok so now im really confused!! More so than before if thats possible.

I just thought i would try one last thing and hooked up a single battery and it works!!!

Its a bit slow but it works. So my question now is why wont it work with 2 batteries as per my original diagram.

Sorry i didnt try this at the start, but at least it gets us talking. And ys i think somone suggested 1 battery so im sorry..
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John W E

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Re: OK so what am i doing wrong???
« Reply #72 on: August 21, 2008, 09:39:13 PM »

Hi there Whiskyfrank

Have you checked the voltage of each individual pack - to see if they are of even voltage?  e.g. 6volts dead on each pack.   Have you checked the voltage in the combined battery packs in the way you wire them up?   to see if it is giving a 12 volts output or slightly more.

Your speed controller should be able to handle 18 volts - although it says it is max 12 volts, but, just to be on the safeside - do not put 18 volts through your speed controller!!!!

aye
john e
bluebird
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DickyD

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Re: OK so what am i doing wrong???
« Reply #73 on: August 21, 2008, 09:44:28 PM »

How about a dodgy battery connection ?
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John W E

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Re: OK so what am i doing wrong???
« Reply #74 on: August 21, 2008, 09:52:39 PM »

10 out of 10 to you Ricard if it is a dry solder joint in the wiring  O0


john
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