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Author Topic: Problem with arduino uno moving giant servos  (Read 3968 times)
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Belgium
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To search I use google (I know about the other thread on links in google pinpointing privacy issues)
Add site:arduino.cc to your search text and you have the best search engine on the world returning only Arduino content at the price of your privacy

To handle the information overload stop reading and start doing. That is what helps with me.

Best regards
Jan
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I just tested it.
google for : giant servos site:arduino.cc/forum
And returned this very thread as very first hit.

Best regards
Jantje
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Dubai, UAE
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Hi,
   I will take that onboard about adding the site to the search, I am not sure that I am in the 'reading not doing' camp though. Its doing that has locked me out of the chips !

Duane B

rcarduino.blogspot.com
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Some one had to do it, so here is a first draft, comments welcome -

http://rcarduino.blogspot.com/2012/03/how-to-connect-servo-to-arduino.html

Duane B

rcarduino.blogspot.com
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the land of sun+snow
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comments welcome -

LOL, I hope you don't take this too critically, as we all have our own
perspectives. You did a lot of work there!

I would have:

1. used a lot fewer words.
2. drawn a couple of schematics, showing 1 servo and many, with special
    mention of power and grounds, servo current loops [lots of current] and
   signal current loops [little current].
3. written a complete Arduino sketch that people could simply cut'n'paste.

But that's just me. :-)
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Some one had to do it, so here is a first draft, comments welcome -

Glad that somebody is interested in providing more info on controlling/powering servos. My observations:

1) Pictures of setups are good, but electrical schematics would provide needed additional technical detail for the servo wiring and power supplies.

2) The idea that a 9v battery with a 7405 regulator chip needs a stronger disclamer that the battery life will be short.

3) The code section is weak, not sure it would be of use to a newbie. Simple copy/paste test code needs to be included instead of relying on more complex code like the sweep example.

4) Information on the various types of servos might be helpful (standard vs continous rotation, etc.).

5) I personally like technical information pages better than narritave blog types of pages.

6) Links to other servo info sites like below might also be helpful.

http://www.lynxmotion.net/viewtopic.php?f=31&t=3172

 

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Guys,

Lots of fair enough comments, but I am surprised about the code example comments, Sweep is available in the IDE 1.0 is it not available in earlier versions ?

As for detailed trouble shooting on the code, I don't think anyone could have a reasonable crack at that, my main intention is to give a method for determining whether its a code problem or a circuit problem, I think creating a test servo in the code that receives no further commands is a good way of loading the circuit with a servo to determine whether the problem is in the code or the power supply/circuit. If its the code, I don't have the mental capacity to second guess half of what gets written out there.

I will leave things as they are for a few days and then rework the whole thing adding some videos of the Arduino driving six or seven servos and some more pictures, diagrams and reworded explanations.

Interestingly I tested with both the LIPO and the 9V battery last night with 3 standard size servos, the 9V was better than I expected, I was able to hold one of the servos in a stall and the system was happy to carry on, I was expecting an instant brown out at stall currents.

Duane B

rcarduino.blogspot.com
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the land of sun+snow
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Interestingly I tested with both the LIPO and the 9V battery last night with 3 standard size servos, the 9V was better than I expected,

"better than I expected" is hardly a "useful" scheme is actual practice, just like
the Arduino tutorial showing a servo connected to the 5V buss. It can be done
isn't the same as recommending a good solution.

First off, hardly anyone will connect just one servo, and secondly, no one
wants their PP9 battery going dead after 10-minutes or so. One needs to
emphasize good portable power sources, such as NiMH AA-cells in a series
arrangement, 2200-2500 mAh and ability to push > 1Amp current, rather than
150 mAh and which will go dead quickly.

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Hi
   Point taken, so while we are all on the subject, can we agree that if someone is unwilling or unable to make the fairly significant additional investment in a hobby quality battery, charger and some form of regulator, the next best option is -

Rechargeable Nimhs in AA, D or C cells
A fall back option is then general AA, D or C cells

With the qualification that the rechargeable Nimhs are more useful in the long run, will often have higher capacity and are able to deliver higher currents.

Duane B.

rcarduino.blogspot.com

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someone is unwilling or unable to make the fairly significant additional investment in a hobby quality battery

Non-rechargeable batteries are so ... 1952 AD, not 2012 AD.

Expensive RC store batteries might be better, but I've been using 2200-2500 mAh
NiMH AA cells bought from Walmart and Target for years on my small robots, with
up to 16 standard servos, and they work fine. I also use 6V SLA batteries on
my heavier robots.

Many people only use Lipo, but that's more preference than actual necessity.

So, you might point out what works good in practice, what sorts of energy levels
they each produce, and what is miserable [eg, Arduino 5V buss, PP9], rather than
trying to sell the case for only what is "best". Engineering is about making good
compromises.
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2200-2500 mAh NiMH AA cells especially those that are rated or recommended for digital camera use are very good general purpose power source for arduino projects. Just series them up for desired output voltage and parallel them up for more duration if desired. They can provide very good peak current loads.

 I will confess that I also still use some non-rechargeable AA alkaline batteries but do buy them in bulk quantities at my local Costco warehouse store, seems to work out to be about 24 cents per cell. Note that your average drugstore wants around $2.50 each for those small 9 volt batteries that 1.50 worth of AA cells would last probably 50 100 times longer, or whatever the math is and would have much larger normal and peak current capacity.

Once educated about it, one should laugh at anyone still using a 9vdc battery in anything other then a smoke alarm or garage door remote or other device that uses just microamps of current.

Lefty

« Last Edit: March 29, 2012, 06:55:59 pm by retrolefty » Logged

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Not sure why all the battery stress. At walmart they have four rechargable AA or AAA batterys with a plugin wall charger for ~$13. Get a holder for the four batterys at radio shack (or DIY one). That should be enough to start tinkering with servos.
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Not sure why all the battery stress. At walmart they have four rechargable AA or AAA batterys with a plugin wall charger for ~$13.

The idea is that, if someone is going to write a page about good practices for
connecting servos to an Arduino, then talking about how to power them should
be a prime concern. Then, noobees won't be trying to power them off the
Arduino 5V buss [like on the Arduino tutorial page] or a PP9 battery, and coming
to the forum to ask why it doesn't work.

Also, be good to talk about different energy sources and their suitability for
powering multiple servos.

Also, buying NiMh AA cells at Walmart has already been suggested 2 or 3 times
on this thread.

These are all suggestions for someone writing a tutorial page on their own.



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Also, buying NiMh AA cells at Walmart has already been suggested 2 or 3 times on this thread.

I only see walmart once previously mentioned, and without a current price point (but maybe it seems like more). Anyhow, a trip to walmart and RS is quick, practical, and easy to do for a quick start.
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Zoomkat
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Also, buying NiMh AA cells at Walmart has already been suggested 2 or 3 times on this thread.

I only see walmart once previously mentioned, and without a current price point (but maybe it seems like more). Anyhow, a trip to walmart and RS is quick, practical, and easy to do for a quick start.
I guess this is true in your part of the world.
In my part there is no wallmart and RS is a "business only" company.

So, you might point out what works good in practice, what sorts of energy levels
they each produce, and what is miserable [eg, Arduino 5V buss, PP9], rather than
trying to sell the case for only what is "best". Engineering is about making good
compromises.

I fully agree with "Engineering is about making good compromises".
I (and I feel many engineers with me) say that for newbees you have to let them focus on 1 problem at the time. Power (in this case batteries) is number 1 in side issue creation.
So I'm proposing to make the compromise of spending to much on the power to allow to focus on 1 problem at the time.
Once it works you can always replace your good power by a cheaper alternative and reuse the good power for your next project.
I'd say it is really worth the money.

Best regards
Jantje
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