ROBOTIC ARM

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Guys, im working on this robotic arm which receives signals wirelessly from a glove which i'll wear on my hand(id probably use some kind of flex sensor). The glove will also have accelerometers to detect the tilt and this data is also sent wirelessly to the uC of the robotic arm.So my objective is that that the robotic arm mimick the exact movements i do with the glove.
1.Which transmitter would you guys recommend?
2.Also, the flex sensor, i did some research and they seem to be a lil expensive and seem to get damaged real easy, is there any other alternative?
thanks :)

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It only been a few days since we had a thread here involving a "sensor glove". There was a link to a University project that looked quite impressive. I'd search this site for "glove" and look at the latest hits..

EDIT: https://courses.cit.cornell.edu/...

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Which part is more important? Making the robot move like the hand, or making it wireless? I bet a half dozen folks might suggest doing it wired first, then just bolt in an xbee module at the end. What is the range? 10 feet? 100 feet? 1000 feet?

Imagecraft compiler user

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I threw a TXM-433-LR and a RXM-433-LR my device for pure simplicity. Tiny, cheap, and baby games to use (complete module, 0 external components besides antenna, no balun on mine). They utilize OOK which stinks as they are really lossy, so I implemented checksums (CRC8 or 16 one day for my device when I learn how to code better). I get a range of about 20 feet on a good day. We built a small-sat a few years ago for U of Mich... I built the radio out of an ADF7020-1 using FSK... worked awesome might I add. If you can't solder as well as me, or don't know jack about radios, don't even bother with any transceiver ICs... go buy a couple Aerocomms or the Zigbees or a Linx Module.

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Quote:
go buy a couple Aerocomms or the Zigbees or a Linx Module.

The flex sensors in the glove give out analog data, so i need to send these exactly to the uC.will that be possible with these modules? Cos i already have an RF module(a434) which has to be provided with a decoder and encoder ic for parallel to serial conversion( the data is therefore digital), so it doesnt really suit my need.

Quote:
Which part is more important? Making the robot move like the hand, or making it wireless? I bet a half dozen folks might suggest doing it wired first, then just bolt in an xbee module at the end. What is the range? 10 feet? 100 feet? 1000 feet?

Both are important. the longer, the better.1000 feet is good.

@JohanEkdahl thanks for the link. :)

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jayakrishnan wrote:
The flex sensors in the glove give out analog data, so i need to send these exactly to the uC.will that be possible with these modules?

Ok... You are going to want your own microcontroller on the glove regardless.

The way I understand it, you have a glove with maybe 5 or more analog output sensors. No plug and play transceiver is going to have more than 2 or 3 ADC channels ready to plug and play and do exactly what you want in one fell swoop. You already will need a voltage regulator on your device, resistors and capacitors for the signal filtering... you might as well slap a Atmega88P 32 pin package on there to finish the job. Again, you will not find a transceiver on the market where you just turn it on and it automatically knows to poll 10 different channels and transmit the data one by one automatically with no configuration, it doesn't exist.

You want to have a micro controller on the glove to do the A/D conversions, to multiplex signals, to send config sets to your transceiver, to regulate power ( I assume you won't want the sensors and radio to run non stop and burn up that battery ) Adding a micro controller will allow you to manage your power, cope with the order you send your data, you will be able to implement checksums or CRC (How were you going to error detect if you only put a radio on your glove?)

1 put a microcontroller on the glove
2 have microcontroller read the data and do AD conversions
3 have microcontroller turn on any of recommended radios
4 have microcontroller send data packets of every signal including your addressing (what if 2 gloves have to run?? is this device just for pirates?), your preamble, your checksums.
5 have microcontroller turn off sensors and radio and go into power down until next data packet needs to be sent.

This surprised me but I was running my linx with no power save options off of 200mAH of battery. I continuously sent data every second with no power down, battery lasted 2 hours running temp sensors, and the radio(how useless). When I got after power management, I am now able to send data every 30mS for 3 days straight off of 120 mAH....

Finally... why would you need a parallel to serial conversion if analog data is what you want to send? You aren't actually thinking of using a Analog to Parallel IC and then a Parallel to Seriel IC????? Why wouldn't you slap one stupid processor the size of a dime on there, throw a recommended module, and be done with it plus get ADC, Serial, I2C, SPI, PowerSaving, Future Button and LED IO options, Etc.... Make sure you get a GHz radio too, they are less Line of Sight dependent and get better range. You want 2.4 GHz probably

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Quote:
You want to have a micro controller on the glove to do the A/D conversions,

Im sorry but if youre going convert it to digital, i really dont think its going to work the way i want it to(correct me if im wrong).suppose a finger moves say, 10 degrees and the flex sensor produces say a value 100 , if im converting it to digital(putting say 200 as base line), everything below 200 will be a digital LOW and above 200 a HIGH.10, 11 ....19 degrees will all be a LOW.so it will be like for everytime i bend my flex sensor more than 20 degree, HIGH will be produced and the robotic arm will bend the finger all the way.. So how can the small changes in the finger movement i do with my hand, be directly mimicked in the robotic arm?

Quote:
Finally... why would you need a parallel to serial conversion if analog data is what you want to send? You aren't actually thinking of using a Analog to Parallel IC and then a Parallel to Seriel IC?????

The A434 transmits only serial data, so i have to convert my data to serial using encoders. And decode them back to parallel at reception.

And, hey thanks a lot for your reply.I really appreciate it. :)

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Quote:

so i need to send these exactly to the uC

It is totally meaningless to talk about "exactly" for analogue values unless you say "how exact". Think a while about the terns accuray and resolution.

Quote:

suppose a finger moves say, 10 degrees and the flex sensor produces say a value 100 , if im converting it to digital(putting say 200 as base line), everything below 200 will be a digital LOW and above 200 a HIGH.10, 11 ....19 degrees will all be a LOW

No, you have misunderstood the basics of an ADC. The ADC converts an analogue voltage to a multi-bit digital value. Example: If your ADC reference is 5.00 Volts and the ADC is set to work with 8-bit values, and you input 5 Volts then the ADC will return 255 (base 10), or 11111111 (binary). If you input 0 Volts it will return 0. If you input 1.23 Volts to the ADC then you will get the digital value 63 (base 10) or 00111110 (binary). (How did I get there? 1.23/5 is 0.246. The maximum value

You are confusing yourself by misunderstanding terms like "digital" to mean "1-bit binary".

Somewhat aside, but still: A device that takes an analogue reference voltage and an analog input voltage, and returns a single digital bit, 1 if the input is higher than the reference - 0 if it is lower, is called an Analog comparator.

As of January 15, 2018, Site fix-up work has begun! Now do your part and report any bugs or deficiencies here

No guarantees, but if we don't report problems they won't get much of  a chance to be fixed! Details/discussions at link given just above.

 

"Some questions have no answers."[C Baird] "There comes a point where the spoon-feeding has to stop and the independent thinking has to start." [C Lawson] "There are always ways to disagree, without being disagreeable."[E Weddington] "Words represent concepts. Use the wrong words, communicate the wrong concept." [J Morin] "Persistence only goes so far if you set yourself up for failure." [Kartman]

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@ JohanEkdahl Thanks for the correction.Cleared a lot of my doubts :)

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How come the overseas guys grasp the idiom of emoticons, but they don't grasp that there is supposed to be one space after a period?

Imagecraft compiler user

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How come youngsters don't even understand periods? Too much effort on the texting machines?

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

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Quote:
that there is supposed to be one space after a period?

And here I thought it was one space after a comma, and two spaces after a period. :roll:

JC

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OT:

bobgardner wrote:
How come the overseas guys grasp the idiom of emoticons, but they don't grasp that there is supposed to be one space after a period?

Are you insinuating that "overseas guys" are worse at English that "non-overseas guys"?

1. "Overseas" from where? G.B.? Madagaskar? :wink:

2. I'd say that the quality of spelling etc among those with English as a native language is about as bad in the U.S..

As of January 15, 2018, Site fix-up work has begun! Now do your part and report any bugs or deficiencies here

No guarantees, but if we don't report problems they won't get much of  a chance to be fixed! Details/discussions at link given just above.

 

"Some questions have no answers."[C Baird] "There comes a point where the spoon-feeding has to stop and the independent thinking has to start." [C Lawson] "There are always ways to disagree, without being disagreeable."[E Weddington] "Words represent concepts. Use the wrong words, communicate the wrong concept." [J Morin] "Persistence only goes so far if you set yourself up for failure." [Kartman]

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you gotta be kidding me -_-'.Out(:P) of curiosity, why do you make such a big fuss out of it? i mean, seriously....!

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OK, this is OT but you did bite:

Quote:
why do you make such a big fuss out of it? i mean, seriously....!

Seriously:
Because it says something about your attention to detail. If English isn't your first, or strong second, language then you are usually forgiven. It is also often possible to identify where spelling misteaks (yes, that was intentional) etc are bacause of dyslexia - that should also be forgiven.

If the reason for repeatedly not captitalizing the first character in a sentence, not capitalizing "I", not getting apostrophes reasonably correct, not caring about punctuation etc is mere lazyness or "don't care" then I see this as not caring about the receiving party.

My judgement of other people is based to some extent to if they care about their language. (Again, if English is not a first or second language, of if it is about e.g. dyslexia, then it's a different thing). I definitively stop reading as soon as I encounter "l33t t4lk" and similar crap.

As of January 15, 2018, Site fix-up work has begun! Now do your part and report any bugs or deficiencies here

No guarantees, but if we don't report problems they won't get much of  a chance to be fixed! Details/discussions at link given just above.

 

"Some questions have no answers."[C Baird] "There comes a point where the spoon-feeding has to stop and the independent thinking has to start." [C Lawson] "There are always ways to disagree, without being disagreeable."[E Weddington] "Words represent concepts. Use the wrong words, communicate the wrong concept." [J Morin] "Persistence only goes so far if you set yourself up for failure." [Kartman]

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Quote:
you gotta be kidding me -_-'.Out(Razz) of curiosity, why do you make such a big fuss out of it? i mean, seriously....!
Not having a space after a period and not starting next sentence with a Capital makes the text much harder to read.
When text is hard to read some of the brain cells that could be used to actually understand the text content instead are used to just read.
New lines now and then also increase readability.
Even a blank line is nice to help the brain do structured reading.

For me personally, finding a post where text miss all that I often react by not reading the post at all.
Not having as many people as possible read your question is your loss, not mine.
My age might be a factor. My eyes might miss the small dot a period consists of. The space and the Capital letter are very helpful.
I'm pretty sure you will loose the attention of many Freaks if you avoid space, Capital letter and new lines.
Does that make any sense to you?

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Oh boy. Looks like i pushed a button. My sincere apologies.

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Quote:
Oh boy. Looks like i pushed a button. My sincere apologies.
No need for apologies..
But if you are so addicted to using AVR Freaks as many of the top posters are (including me) we read hundreds of posts every day, and the ability to do the reading without too much effort makes a huge difference (at least for me).
I.e. I skipped over your question and would have moved on to another thread if you'd not made the post I replied to.
I took the time to reply cause I thought you might be sincerely interested in the answer.
Have I wasted my time?

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And all those billions of dollars pooring into MS headquarters and I.E. still can't do spell checking for me...

JC

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It can check if the incorrect word you chose is spelled correctly though.

Imagecraft compiler user

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Hello to Jayakrishnan. Do you get the idea that the experienced engineers are suggesting that the glove is a module that communicates with the robotic appendage? (I didnt call it an arm because that is an unfortunate overloading of a perfectly unambiguous English word until it was used by the Acrorn Risc Machine.) Anyway, this is the domain of system engineering. You need to design for reliability, maintainability, and whatever Figures Of Merit your boss requires, like cost effectiveness. If the glove outputs an RS232 stream at 115200 bps with a simple protocol that specifies the angle of each finger with a byte or two, you could get Real Time gripping on the gripper. Do you want to get any Force Feedback from the gripper when the object is in the fingers?
With a Closed Loop feecback, you could pick up an egg. But you need two way communication from the hand to the arm, and back from the arm to the hand.

Imagecraft compiler user

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DocJC wrote:
Quote:
that there is supposed to be one space after a period?

And here I thought it was one space after a comma, and two spaces after a period. :roll:

JC

I heard on my BBC/NPR yesterday that a comma and period are both followed by a single space nowadays. The reason for the double space after the period is a relic from the days of a typewriter where all the letters were the same width so a 'l' followed by an 'l' would have a space between the letters even though it wasn't intended. By putting a double space for every space, there was no mistaking a new sentence and made it more readable. With the advent of modern typewriters and the PC, the width of letters and spaces are now set up appropriately so we only need one space. Thought it was funny to hear this convo on here just after listening to it on the radio =)

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Oh man!

Second time today I've been called or inferred to be an Old Timer.

Next thing you know the New AVR Freaks Forum will have a separate section for AARP members. "I know the STK1000 runs under AVR Studio 12, but I'm still using my Mega8515 under A.S. 4.19 ..." :wink:

JC

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I can't run anything later than AVR Studio, 4.18.700... Nothing compiles on my brand new computer in anything other than this version so whatever

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I recommend that you walk before attempting to run. Why not start by trying to get a simple step motor to respond to proportionally to a sensor over a wired connection. That sounds simple, but it is really quite complex. Once that is working, then substitute the wired link with a pair of nRf2401 2.4GHz wireless transceivers. Many more complexities to muddle through, but it will work for ranges up to 10m or more.

Then, increment by increment, work your way up to what you are talking about.

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Quote:
two spaces after a period.

That was the case when we used typewriters. These days the software is supposed to adjust the spaces according to various rules, not on a forum of course because it's essentially plane text, but with proper layout programs.

So I guess you could argue the case for two spaces here, but one is good enough.

Quote:
check if the incorrect word you chose is spelled correctly though.

Like I just done above, were I used a word that was just plane wrong :)

______
Rob

Scattered showers my arse -- Noah, 2348BC.
Rob Gray, old fart, nature photographer, embedded hardware/software designer, and serial motorhome builder, www.robgray.com

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Thanks, to everyone who replied. I found this transceiver and it was pretty cheap too. What do you guys think?

http://www.robosoftsystems.co.in...

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Quote:
Hello to Jayakrishnan. Do you get the idea that the experienced engineers are suggesting that the glove is a module that communicates with the robotic appendage? (I didnt call it an arm because that is an unfortunate overloading of a perfectly unambiguous English word until it was used by the Acrorn Risc Machine.) Anyway, this is the domain of system engineering. You need to design for reliability, maintainability, and whatever Figures Of Merit your boss requires, like cost effectiveness. If the glove outputs an RS232 stream at 115200 bps with a simple protocol that specifies the angle of each finger with a byte or two, you could get Real Time gripping on the gripper. Do you want to get any Force Feedback from the gripper when the object is in the fingers?
With a Closed Loop feecback, you could pick up an egg. But you need two way communication from the hand to the arm, and back from the arm to the hand.

That is a lot of baud rate, can i get that much for transceivers (cheap ones)?
And how do i build a closed loop system?

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Quote:
I took the time to reply cause I thought you might be sincerely interested in the answer.
Have I wasted my time?

Not at all. Please do give me your opinion. Thankyou

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Since my laptop can read and write at several tens of megabits per second wirelessly, I'd say that the speed of the rf link is not the bottleneck in this project. I have a couple of xbee modules, and the manual shows you can select 115200 or a custom rate.

Imagecraft compiler user

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jayakrishnan wrote:

And how do i build a closed loop system?

Closed loop systems are one of two types of controls systems.

Closed loop requires two way communication. A command is sent to a motor/actuator for the machine to move. A sensor measures the actual motion the motor moved and sends that information back. Hence the two sides talk to each other and fix overshoot or undershoot mistakes (servo rotates .05 degrees too far or whatever...). If you have your analog output rotation sensors on the glove with a motor, and the glove can receive and send data to some computer, you have already "built" your closed loop system.

If I were you I'd start with a full blown PID Closed Loop System and work up from there =) (jokingly)