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Offline rhey22Topic starter

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problem running 3 IRs simultaneously
« on: February 15, 2009, 09:27:10 AM »
Hello,

Our group is trying to use 3 IR sensors simultaneously and output their readings in hyperterminal. We are using axon microcontroller and the sensors were already attached to our biped robot. We are having problems making the 3 sensors work at the same time. First, it was "Failed" when we upload the code to axon and the green LED lights. Though there was this one time when it loaded successfully, the green led still lights on and no readings are seen on the hyperterminal. After a successful load again, it did output values on the hyperterminal but for a short period only. Below is the readings we got:

System Warming Up.................Initialization Complete
 front, right, left = 29, 18, 26
 front, right, left = 30, 18, 25
System Warming Up.................Initialization Complete
 front, right, left = 30, 18, 26
System Warming Up.................Initialization Complete
 front, right, left = 30, 19, 26
 front, right, left = 34, 18, 25
 front, right, left = 30, 18, 25
System Warming Up.....


We tried to test each IR sensor separately and it went well, all sensors are in good condition. Once we attached the other sensors, the problem comes in. Even if no codes were used and just plug in the sensors then turn on the axon, the green led still flashes. Is this unusual? What could be the problem?

Any help would be greatly appreciated..Thanks

Offline Soeren

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Re: problem running 3 IRs simultaneously
« Reply #1 on: February 15, 2009, 01:28:42 PM »
Hi,

What kind of IR sensors?

If they are the Sharp PSD's, and they point roughly towards the same point, they will see each others modulated IR and will not be able to be on concurrently.
In that case, use them one by one - get a (couple of) reading(s) and skip to the next.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
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Offline cosminprund

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Re: problem running 3 IRs simultaneously
« Reply #2 on: February 15, 2009, 01:41:29 PM »
The message "System Warming Up.................Initialization Complete" means the Axon is restarting. The blinking green light also points in the same direction (that green light stays on only for 0.3 seconds after boot).

There was a thread around here recently about the same problem, with 3 IR range finders + Axon. The solution was to add some capacitors near the sensors. I tried finding the thread but failed :(

Offline rhey22Topic starter

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Re: problem running 3 IRs simultaneously
« Reply #3 on: February 15, 2009, 08:12:28 PM »
Thanks for the replies.

We are using Sharp GP2D12 IR sensor for the obstacle avoidance of our robot. The sensors were positioned at the front, right, and left side of the robot. The thing is even if we did not use the sensors and implement no codes for it and just left it attached to the axon, the axon still resets. The green led is not just blinking but is constantly on. Why is this so? ???


Offline householdutensils

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Re: problem running 3 IRs simultaneously
« Reply #4 on: February 15, 2009, 08:58:01 PM »
Disregard this post, I didn't read your initial post properly.
« Last Edit: February 15, 2009, 09:11:58 PM by householdutensils »

Offline ArcMan

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Re: problem running 3 IRs simultaneously
« Reply #5 on: February 15, 2009, 10:12:41 PM »
Hmmm.  From everything said on this post, I'm wondering if you have a power problem.  Try measuring your supply voltage when all 3 sensors are connected.

Offline yerbie

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Re: problem running 3 IRs simultaneously
« Reply #6 on: February 16, 2009, 08:24:40 AM »
The message "System Warming Up.................Initialization Complete" means the Axon is restarting. The blinking green light also points in the same direction (that green light stays on only for 0.3 seconds after boot).

There was a thread around here recently about the same problem, with 3 IR range finders + Axon. The solution was to add some capacitors near the sensors. I tried finding the thread but failed :(


This is what you're looking for:
http://www.societyofrobots.com/robotforum/index.php?topic=5190.0
http://www.societyofrobots.com/robotforum/index.php?topic=6734.0

Offline rhey22Topic starter

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Re: problem running 3 IRs simultaneously
« Reply #7 on: February 23, 2009, 03:23:45 AM »
Thanks for the links.
We will try to mount a 10nf in parallel with a 510 ohm resistor to the Sharp IR sensor. We will try also the other option which is placing a 10uF capacitor across the adc power and ground. Is is ok if we use a 10uF electrolytic capacitor instead of a ceramic capacitor?.

Offline Tomas

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Re: problem running 3 IRs simultaneously
« Reply #8 on: February 23, 2009, 06:25:13 AM »
Thanks for the PM. If you are experiencing resets, then you may want to try downgrading to source code 1.01. I've had some problems with 1.05 (I have not tested 1.06b yet).

Are you by any chance seeing the message "called bad ISR" or parts of it in hyperterminal? If so, downgrading will be successfull. Try downgrading to 1.01 anyway, as I said, Ive had some "ripping my hair out" moments with 1.05....

And you placed the  capacitator between + and -, and not - and signal?

Also, I didn't hook up a resistor in my sharp ir sensors, I only used a small, fast capacitator. It's very important that its fast (I dont remember if its electrolytic or ceramic which is fastest).
« Last Edit: February 23, 2009, 06:26:39 AM by Tomas »

Offline rhey22Topic starter

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Re: problem running 3 IRs simultaneously
« Reply #9 on: February 23, 2009, 06:44:56 AM »
We are not seeing message like "called bad ISR" in the hyperterminal. What happens is that there are times when it failed loading the code to the axon and when it loaded successfully, the hyperterminal output values for about 2 to 3 lines/readings only and "System warming up" appears with the green LED constantly lit.

We placed the capacitor between the output signal(yellow wire) and ground of the IR sensor as suggested by Admin in http://www.societyofrobots.com/axon/axon_FAQ.shtml#sharp_ir_reset..
 

Offline airman00

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Re: problem running 3 IRs simultaneously
« Reply #10 on: February 23, 2009, 06:51:43 AM »
no no

10uF or higher capacitor between ADC power and ground  - between red of the ADC and ground.
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Offline rhey22Topic starter

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Re: problem running 3 IRs simultaneously
« Reply #11 on: February 23, 2009, 07:08:14 AM »
What we tried is the second solution suggested by Admin. We haven't had the chance to try the first solution which is placing 10uF or higher capacitor between ADC power and ground. We're not able to find 10uF ceramic capacitor and instead what we have is the 10uF electrolytic capacitor. We're not sure if using electrolytic capacitor will be just fine so we didn't try it. Will it be ok if we use it instead of a ceramic one?

Offline paulstreats

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Re: problem running 3 IRs simultaneously
« Reply #12 on: February 23, 2009, 07:17:04 AM »
electrolytic is fine (I think that he may have made an error saying ceramic)

Offline airman00

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Re: problem running 3 IRs simultaneously
« Reply #13 on: February 23, 2009, 08:08:09 AM »
just make sure you connect the electrolytic capacitor in the correct direction ( look on the capacitor to see which way is negative)
Check out the Roboduino, Arduino-compatible board!


Link: http://curiousinventor.com/kits/roboduino

www.Narobo.com

Offline rhey22Topic starter

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Re: problem running 3 IRs simultaneously
« Reply #14 on: February 23, 2009, 09:00:42 AM »
Ok we'll try then the 10uF electrolytic capacitor but maybe tomorrow. I'm not with the group already and we'll continue working on it tomorrow. Hope this one would work already. Thanks for the help..

Offline paulstreats

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Re: problem running 3 IRs simultaneously
« Reply #15 on: February 23, 2009, 05:39:13 PM »
It might help to fit a small ceramic capacitor as well (probably not as high as 10uf though).

Ceramic capacitors react faster than electrolytic so if you are suffering from sudden power drop, the ceramic will take the strain until the electrolytic has time to kick in...

Offline rhey22Topic starter

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Re: problem running 3 IRs simultaneously
« Reply #16 on: February 23, 2009, 07:29:31 PM »
It might help to fit a small ceramic capacitor as well (probably not as high as 10uf though).

Is the ceramic capacitor in parallel with the 10uF electrolytic cap?Is a 10nF ceramic ok?
Thanks..

Offline HDL_CinC_Dragon

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Re: problem running 3 IRs simultaneously
« Reply #17 on: February 23, 2009, 07:36:59 PM »
Electrolytic caps are usually used near low frequency devices such as motors. Ceramics are used near high frequency components such as sensors.

-EDIT-
Capacitors in parallel add up like resistors in series.
« Last Edit: February 23, 2009, 07:39:33 PM by HDL_CinC_Dragon »
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Offline rhey22Topic starter

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Re: problem running 3 IRs simultaneously
« Reply #18 on: February 24, 2009, 10:33:07 AM »
I'm sorry for the double post.. :-[

Anyways, we tried already placing a 10uF electrolytic capacitor across the adc power and ground, and the axon stopped resetting when connected with 3 IRs. It works fine already.. :D

Thanks again for all the replies, suggestions, and help.. :)

Offline paulstreats

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Re: problem running 3 IRs simultaneously
« Reply #19 on: February 24, 2009, 11:36:17 AM »
If you add more sensors or other stuff then you may also have top add more capacitors to help the power system along

Offline Admin

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Re: problem running 3 IRs simultaneously
« Reply #20 on: February 25, 2009, 10:36:29 AM »
The noise in the Sharp IR is low frequency, so the electrolytic will work fine.

If you really want to optimize it, hook it up to an oscope and see what capacitor types/values give you the best noise reduction.

 


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