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Author Topic: Counter for rubber winder  (Read 1485 times)
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msc
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« Reply #25 on: February 20, 2017, 08:18:49 PM »

Thanks for sharing the schematic. It makes it much easier to see how you handled the details. There are a few things that did not come through clear enough to read so I have a couple questions.

What battery type did you use?
Is your VCC voltage 3.3V or 5V?
What regulator chip are you using?
What RTC are you using?

My interest is mostly technical curiosity. A large part of my day job is the design and fabrication of special purpose data recording and control equipment for various research projects. I do a lot of hardware design but have only dabbled a bit with programming.

Mike
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msc
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« Reply #26 on: February 20, 2017, 08:22:16 PM »

My plan is to use 3 hall sensors for positive tracking of the direction of each rotation. This of course allows automatic counting of the peek turns and the windback turns. If more then a couple minutes go by and then more turns are backed off they are assumed to be the count of remaining turns at the end of a flight.

For any models where the rubber is wound off of the model the torque gauges based on an electronic scale are difficult to improve on. To display or log the torque on the counter display the easy solution is to make a custom electronic module that connects to the same load cell but in addition to displaying at the scale would broadcast to the counter over a bluetooth connection. When doing custom electronics a couple other nice features are easy to add. The auto shutoff time can be set as long as desired and it can be easy to select between In/oz and g/cm for scaling.

When the motor is wound on/in the model it becomes trickier to monitor/log torque but it can be done. It would require a sensor module installed on the output shaft of the winder much like the twist wire torque gauges. It's a much greater challenge to design but should fit on a circuit board about 2 inches in diameter. With a rotating sensor the beam type load cell from a cheap scale would no longer work so a true torque load cell would need to be custom fabricated. Powering and communicating with the sensor is the significant challenge. Slip rings are possible but would have to be very precise to have acceptable drag and be reliable. Battery powered and wireless data link is more practical but who wants another battery that needs to be maintained. Inductive power coupling with Bluetooth data is probably the best approach but adds another system to develop.

It's just a design concept at this point that may or may not ever happen. I am using it as a motivation to do some tinkering with programing micro controllers. I have purchased some sensors to play with and have been re-familiarizing myself with some programming tools.

I'll be starting out with Arduino because I have worked with them in the past and I can get the environment to run on my vintage Mac. There are lots of compatible building block modules with extensive support libraries so it should be straight forward to experiment with bluetooth and SD cards. The initial work will be mostly with available modules tied together with breadboard construction. After getting code running and hardware features finalized circuit boards would be laid out for final packaging. At that point it may be best to ditch the Arduino environment but I'll have to weigh any expected benefits against another learning curve.

If I get a decent start on development I'll start a thread to give updates on progress and seek feedback on features.

Mike
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rgroener
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« Reply #27 on: February 21, 2017, 01:43:42 AM »

Mike, good news that you are on your way.

To your questions.

I use a single cell (1.2V Accu or 1.5V Batty) as power source. The TPS61220 will boost it up to 3.3V. So VCC is 3.3V since the display needs 3.3V, no additional voltage converters are needed.
- TPS boost converter TPS61220 http://www.ti.com/lit/ds/symlink/tps61222.pdf
- The RTC is a MCP7941 http://ww1.microchip.com/downloads/en/DeviceDoc/20002266F.pdf
- Hall sensor is a SS443A http://www.mouser.com/ds/2/187/honeywell-sensing-ss400%20series-product-sheet-00905-947400.pdf

About the detecting of the direction... why do you want to use 3 hall sensors? Wouldn't two be enough?

Good idea about measuring the torque. I never thought on using an electronic scale.
The problem with my ideas on measuring the torque was always the turning part of the winder which would turn the sensor and therefore also the cabling.
Wile reading your post, I maybe have a solution for my problem. I have to think about it and will write more as soon as I see that it could work.
I am still looking forward to your solution.

Arduino is a good solution especially if you used it before. I never used them, but the Arduino Uno board has the same processor I am using. Its also an Atmega328p.
Therefore it would be easy to use it in your follow up project without the arduino hardware.

If you like to skip the Arduino step, I could offer you one of my prints. I would also share my code, including the library for the display. It's just an offer, you can decide what's easier for you.
The programming environment is also available for Mac. An apprentice of mine uses it on his privat mac.
Look here for some install instructions http://www.ladyada.net/learn/avr/setup-mac.html

From my side, you dont have to open a new thread. If you want so, it's fine too. Feel free whatever you want Grin

Roman







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Tapio Linkosalo
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« Reply #28 on: February 21, 2017, 01:55:37 AM »


I've been considering the means of measuring torque while winding, and have had rather similar thoughts as Mike. However I have another issue for which I have yet to find any working solution- I would like to measure also the stretch of the rubber motor while winding, but have not figured out any working and yet accurate enough system to find out the distance from winder to torque meter. Laser/light would be accurate, but would need extremely fast time measurement. Ultrasound might work, but would probably need some active system, as the passive sensors are not accurate enough. Mechanical systems - prone to tangle!


-Tapio-
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rgroener
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« Reply #29 on: February 22, 2017, 12:48:46 AM »

Tapio, what do you mean by an active ultrasound system. Ultrasound is always acitve, isn't it? You need a transmitter and a receiver. I would start with something like this.
http://www.micropik.com/PDF/HCSR04.pdf
Maybe you would have to add a plate at your winding stooge to make sure that the ultrasound impuls is reflected nicely.

Roman
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Tapio Linkosalo
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« Reply #30 on: February 22, 2017, 01:15:22 AM »


By "active" system I mean a setup  where instead of a passive reflector plate I'd use an active "repeater" to give a strong precise signal from the other (passive) end. In simplicity, this could just a device that is listening to a certain frequency and starts emitting sound when it is receiving sound. Tuning down the receiving sensitivity of the measuring end so that it does not "hear" the reflections, only the actively sending repeater, I could exactly pinpoint the reflection coming from the point I intend. And therefore would get much better accuracy of the distance, just would have to account for difference in sound speed due to temperature and pressure variations. But, this would mean hacking into the systems and writing some specific code for them...

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Andrew Darby
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« Reply #31 on: February 22, 2017, 02:26:42 AM »

Since "every action has an equal and opposite reaction" I don't think that you don't need to measure the torque at the winder, simply measure it at the stooge.  So long as the model is not touching anywhere else and the axis of the rubber is at right angles to the measuring "arm" then the torque in the rubber would be the reaction at the rear peg....

Andrew
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Hogwash I tell thee!
Tapio Linkosalo
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« Reply #32 on: February 22, 2017, 03:38:10 AM »

Applies for indoor models, or if you are winding the motor in modern fashion outside the model with a half-tube. But not for outdoor winding inside the model, where the wing is impacting the model.

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