### Author Topic: Sensor Array  (Read 3189 times)

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#### w_bwr

• Jr. Member
• Posts: 18
##### Sensor Array
« on: May 13, 2010, 12:34:17 PM »
i have made ir sensor circuit for white line following. the single cell works well. but when i tried to use 4 cells, with LM324 using single pot for calibrating, the problem is all the bits appear high by giving signal on a single cell.
i used the same schematic given in this site in the section "ir sensor".
&
what is Hysteresis in the sensor circuit. how can i use it by lM339?

#### Soeren

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##### Re: Sensor Array
« Reply #1 on: May 13, 2010, 01:00:03 PM »
Hi,

You really have to post an exact schematic of your circuit for aqnyone to help.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Engineering is based on numbers - not adjectives

#### w_bwr

• Jr. Member
• Posts: 18
##### Re: Sensor Array
« Reply #2 on: May 13, 2010, 01:52:56 PM »
I have uploaded a rough schematic, hope you would have an idea what i 'm making....

R1 = 150 ohms
R2= 5k POT
R3 = 4.7 Kohms
R4 = 10 Kohms
IC = LM324

or
suggest any other schematic that can be used using single pot!
« Last Edit: May 13, 2010, 03:18:34 PM by w_bwr »

#### Soeren

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##### Re: Sensor Array
« Reply #3 on: May 13, 2010, 05:01:23 PM »
Hi,

I have uploaded a rough schematic, hope you would have an idea what i 'm making....
[...]
IC = LM324

or
suggest any other schematic that can be used using single pot!

There are a couple of issues with your circuit.
First off, you shouldn't short circuit the outputs of an LM324, it is a quad op-amp and it has got push pull outputs. The LM339 is a quad comparator and it has got open collector outputs, which can be shorted together without problems. The LM339 outputs needs a pull up resistor as well.

Second, you are shorting all the non-inverting inputs, so if one or more of the photo transistors  gives enough current through, it will affect all the op-amps, as they won't function as indepentant amps coupled like that.

The negative feedback (giving hysteresis) will affect all amps as well.
Hysteresis is the effect where you change the shifting point of the circuit, by leading a part of the output signal to the inverting input. With a hysteresis of eg. 100 mV and a shifting point of 2V going upwards will then change the shifting point to 1.9V that it must go under to switch back to the 2V. This is done to avoid an unstable situation where it oscillates around the shifting point.

The circuit you have (seen for just a single amp) is a bit strange, as with the output low, will have a shifting point of 0V and when the output is high, the point will be ~1/3 Vcc.

I don't know why you shorted the outputs together, since the point in having more than one detector is to be able to tell which of them see a line, but that takes separate outputs fed to the rest of the circuitry used for the 'bot.
To change the circuit into something useable, you need a bit more resistors, to break it into separate inputs, outputs and feedback.

Using a single pot, it would be easier to place it in the inverting inputs circuit.

What will the outputs go to?
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Engineering is based on numbers - not adjectives

#### w_bwr

• Jr. Member
• Posts: 18
##### Re: Sensor Array
« Reply #4 on: May 14, 2010, 05:27:06 AM »
outputs will go to ATmega16,
and the controller will control the H-bridge!!!!

#### Razor Concepts

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##### Re: Sensor Array
« Reply #5 on: May 14, 2010, 06:19:06 AM »
But all of your outputs are connected. So they will always be at the same state, and the data will be useless.

#### Soeren

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##### Re: Sensor Array
« Reply #6 on: May 14, 2010, 09:37:28 PM »
Hi,

This circuit should help.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Engineering is based on numbers - not adjectives

• Jr. Member
• Posts: 18