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Electronics => Electronics => Topic started by: Bret on December 04, 2008, 10:03:21 AM

Title: Sharp IR Range Finder Problems
Post by: Bret on December 04, 2008, 10:03:21 AM
The problem I was having last week is back!

The problem is:
I have two Sharp IR Range finders. If I plug one in it works great. If I plug the other in it works for a few seconds then resets my Axon. This happens a few times and then it completely locks up. It also starts running my program without me initiating it by pressing the Axon button to start my program.

What I have done to fix/narrow down the problem:
I purchased two 6V 2300mAh battery and smart battery charger from All-Battery.com. I got two of them so that I can charge one while I recharge the other. It does the same thing with both batteries. I have checked the current and the voltage and they look good now. I got the 5 photoresistor package from Radioshack and put my own light sensors together and I can plug all five in and get good readings. I can even have all 5 of my light sensor plugged in with a Sharp IR Range Finder and it works great, but if I plug in the second Range Finder it starts misbehaving again. I also simplified the program so that it does nothing but update the sensors and print the data to Hyperterminal.

Something I am trying to correct the problem:
I am getting a couple of 10uF capacitors to place between Vcc and ground. It recommends one in the data sheet.

Here is a parts list of the items I am using:

Toward the end of last week I reported this error fixed because everything began working well for a few hours, but after that it quit working and I have been trying to find out what is going on without bugging everyone, but at this point I'm all out of ideas, other than the 10uF capacitors I plan to install.

Could it be something in my program?
I'm thinking not because my light sensors work.

Could it be something with this particular model of Sharp IR?
I've noticed that the part number is odd and the GP2D12 is more commonly used.

I don't think I'm drawing enough mA to be a problem since I have been only testing it with the Axon and the two Range Finders, without a servo to cause any real mA draw.

Thanks for any assistance that you can give!
Title: Re: Sharp IR Range Finder Problems
Post by: Robotics Guy on December 04, 2008, 10:10:09 AM
I've never used that sensor before, and without seeing your code can't tell you if it's a problem with your program, but in the past I've found when using multiple sensors of the same type they sometimes need to be daisy-chained to work properly.

Maybe you can check with the manufacturer.
Title: Re: Sharp IR Range Finder Problems
Post by: airman00 on December 04, 2008, 10:13:34 AM
which pin are you connecting the Sharp IR sensor to?

also sounds like it might be shorting out
Title: Re: Sharp IR Range Finder Problems
Post by: Bret on December 04, 2008, 10:41:35 AM
Thanks Robotics Guy and Airman00!

Robotics Guy -
I don't think my problem is software because I can hook my light sensor to the same pins and it works fine. I think if it were a code problem then it would misbehave no matter what I hooked up. Of coarse I've been known to do odd things with code before  :-[ . When you say to 'daisy chain' the sensors together are you talking about coming out with power to the first sensor then hooking the ground lead of that sensor to the power lead of the other sensor then returning to ground with the second sensor's ground lead with each data lead going to it's respective pin on my Axon? That could certainly be worth trying.

Airman00 -
Per the labeling on the Axon I am connecting one IR to ADC(0) and the other to ADC(15) (F-0 and K-8). If it's a short then it only happens when both IRs are connected and it doesn't seem to care where I connect them. Either IR works fine on it's own, or even with all my photoresistor sensors.

This problem is bugging the heck out of me because it's only a 1-5 volt signal, just like the sensors that I put together. What could it be about the IR that is different with respect to the Microcontroller? I mean, from the Microcontrollers standpoint it is just feeding the device 5 volts and getting back a 1 to 5 volt signal on the input pin - just like the sensors I put together. Am I thinking about this wrong? I just can't figure out what the difference is. Grrrrrrr....  >:(

Title: Re: Sharp IR Range Finder Problems
Post by: brijesh on December 04, 2008, 01:45:22 PM
I think you have similar issue as in this post.

http://www.societyofrobots.com/robotforum/index.php?topic=5190.0

Title: Re: Sharp IR Range Finder Problems
Post by: Bret on December 04, 2008, 02:24:11 PM
Thank you brijesh!

That sounds like the exact same problem I am having!

I already ordered the 10uF capacitors this morning so as soon as they come in I will let you know if that fixed my problem also.