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Attempt at cheap homemade version of Harmony
#51
I am a neophyte.

I remember a year ago when Normand tried to educate and help me understand the PID . Ouf poor guy... he is patient, let me tell you this. (For an number of other reasons...)

He was quoting Ziegler-Nichols method as it is easy to understand and showed me a graph of a typical curve. I know on my old bicycle I need to overshoot to change gear. Cable rub/strech, worn out bushing etc...

Thanks for sharing.
Avant de le savoir, je l'ignorais...
(antequam sciat ego nescibam)
-  watageek
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#52
I have a question;

Have you think going on stmicro or else (silab,etc) chip instead of atmega. I am thinking of the F1 series with a SPI bus. They have 4 lane.


One of my friend suggest I should invest time in C and C++... I couldn't agree more.
Avant de le savoir, je l'ignorais...
(antequam sciat ego nescibam)
-  watageek
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#53
Sorry has been a while since I looked at the forum. Did you make a bicycle with automatic shifting? 
I haven't yet looked into PID as I haven't needed to, my current version of the code is working nicely. At the moment I'm learning about strain gauges for a bicycle power meter project I will write about soon on here.

Was not aware of ST microcontrollers it appears they have an extensive range to choose from. Think I'll stick with the Arduinos for the current prototype but if I make a higher performance more finished version st micro look like the way to go.
- Oran
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#54
Making the auto shifter self sufficient.
The lipo lasts for about 150 – 200 miles which is OK but I finally got round to make it self sufficient well almost.

[Image: 4kD4xd.jpg]

To start with I have connected the dynamo direct to the 11.1V lipo well through a rectifier and the protection circuit. With the 700c wheel it outputs a volt per mph (1.6kph) so won’t start charging until about at least 12 – 13 mph ( 20kph). Due to the voltage being double it’s rated, the power output with sufficient speed should also be double. Initial results are as expected if I maintain a high average speed it will put a little charge into the battery. If not such as city riding it can’t keep up with the demand.

I’d like it to be capable of generating more than I need so that I can program the Arduino to switch it off in certain situations such as when my power output is high. To do this some sort of boost / MPPT circuit will be required and an Arduino compatible MOSFET Driver Module. I’d like to avoid extra circuits if I can so I’m going to try reducing the battery voltage to a 2 cell (7.2V). Less power but will generate at a lower speed so for longer.
- Oran
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#55
(08-11-2017, 01:58 PM)Oran a écrit : Did you make a bicycle with automatic shifting? 

No sorry, I was referring to the strech of the cable and the "magic touch" you need to have to change gear on old bikes
Avant de le savoir, je l'ignorais...
(antequam sciat ego nescibam)
-  watageek
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#56
(08-18-2017, 01:06 PM)Oran a écrit : Making the auto shifter self sufficient.
The lipo lasts for about 150 – 200 miles which is OK but I finally got round to make it self sufficient well almost.


Just by curiosity, you are using a switching LDO to drive the servo? Just a tought.
Much more efficient than a (linear) regulator. you didn't specify otherwise than industrial.
Maybe servo with more torque.


I don't know much thing. I' m curious.
Avant de le savoir, je l'ignorais...
(antequam sciat ego nescibam)
-  watageek
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#57
(09-03-2017, 12:38 AM)watageek a écrit : Just by curiosity, you are using a switching LDO to drive the servo? Just a tought.
Much more efficient than a (linear) regulator. you didn't specify otherwise than industrial.
Maybe servo with more torque.  


I don't know much thing. I' m curious.

Don't know about Oran's setup, but a 2 cells Lipo does not need regulation and can be plugged directly on most modern servos (They can run from 3,3v to about 7 or 8 volts without issue)

EDIT:
I just re-read Oran's post, he is on 12volt (3-cells) Lipo but plans reducing it to 2 cells Lipo
He is talking about MTTP, wich is as type of charging regulator that is simple yet efficient but I was not aware that it could be used on LiPo packs!
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#58
(09-03-2017, 12:25 AM)watageek a écrit : No sorry, I was referring to the strech of the cable and the "magic touch" you need to have to change gear on old bikes

Watageek, Oran's bike and mine do not have "gears" so to speak... We are both using NuVinci CVT transmission on our bicycle!
This gives seamless "shifting" and infinite ratios in a given range... 
he tradeoff is a little loss in efficiency due to friction, but pedaling at your bio-pace at all times overcomes this loss most of the time.
[Image: nuvinci_002.jpg][Image: nuvinci_003.jpg]


You can read a little more on my setup in this post:
http://normandnadon.com/forum/showthread.php?tid=401

and this one too:
http://normandnadon.com/forum/showthread.php?tid=744
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#59
Watageek, I know want you mean by the “magic touch”, I used to be very good at it before I got a CVT. Always preferred thumb shifters and would sometimes use them without the indexing.
Both of you have come up with very useful suggestions. I don’t know what the efficiency of the voltage step down 5V supply is. It’s all potted into an aluminium heat sink. Could be inefficient with low current output, at the time I just wanted something with a high current output. Makes sense to me as well that a higher torque servo could be more efficient. It will spend less time trying to get to where it’s meant to be.

Normand, how confident are you that the servo won’t mind 8.4V? Would be great to get rid of the bulky 5V supply. If I switched to a 2 cell battery I’ll be using 2 x 18650s because I’ve got lots of them from old laptop batteries. A few of them passed my tests and have a reasonable capacity left. I prefer 18650s, they are more compact, safer and when new have a higher energy density. 

Could be a big improvement in the design. Direct charging from the dynamo at above 9 mph  (14 kph), efficient power for the servo, more torque from the servo and far more compact design ( 2 x 18650 battery box, 2 Arduinos, BT module and a switch). Might be room in the saddle bag for a spare inner tube or the beginning of moving the Arduinos to somewhere else on the bike.
- Oran
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#60
(09-05-2017, 10:07 AM)Oran a écrit : Watageek, I know want you mean by the “magic touch”, I used to be very good at it before I got a CVT. Always preferred thumb shifters and would sometimes use them without the indexing.
Both of you have come up with very useful suggestions. I don’t know what the efficiency of the voltage step down 5V supply is. It’s all potted into an aluminium heat sink. Could be inefficient with low current output, at the time I just wanted something with a high current output. Makes sense to me as well that a higher torque servo could be more efficient. It will spend less time trying to get to where it’s meant to be.

Normand, how confident are you that the servo won’t mind 8.4V? Would be great to get rid of the bulky 5V supply. If I switched to a 2 cell battery I’ll be using 2 x 18650s because I’ve got lots of them from old laptop batteries. A few of them passed my tests and have a reasonable capacity left. I prefer 18650s, they are more compact, safer and when new have a higher energy density. 

Could be a big improvement in the design. Direct charging from the dynamo at above 9 mph  (14 kph), efficient power for the servo, more torque from the servo and far more compact design ( 2 x 18650 battery box, 2 Arduinos, BT module and a switch). Might be room in the saddle bag for a spare inner tube or the beginning of moving the Arduinos to somewhere else on the bike.

Can't tell about your particular servo... HobbyKing sells servo specially marked as "HV servos" that can run on 7,4 volt nominal batteries
I ran my servo on my own bike with 2 lipo cells for a short while, but I found it to be too fast. Reduced to a direct driven servo on a single cell (no feedback electronic). No intelligence there!

Some servos have electronic that is sensitive to voltage past 5,5volt... But most digital can take much more.

There is also the option to put a high efficiency UBEC to drive only the servo...
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Si ça a déjà été fait, je peux le faire
Si ça n'a jamais été fait, donnez-moi juste le temps de trouver comment !


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