# perform automatic function

#### karthiksrao

Joined Oct 21, 2006
3
hi..
i'm completing my engg degree in mechanical field.. We were asked to do a project in mechatronics..

The problem statement goes like this... the number of objects passing on a conveyer belt has to be sensed.. when the number has crossed a certain limit ... a signal has to be sent to the motor to stop the conveyor belt...

I guess a led would do the trick for sensing the objects.. apart from that i have absolutely no clue , how to go about doing this..Please help me with the circuit to build this model...We've had a basic course in electonics. So i'll be able to understand the basic components in an electronic circuit...

We've been given liberty to buy any standard unit that is available in the market.. also we've got to complete this in a week's time...

karthik.

#### Papabravo

Joined Feb 24, 2006
20,162
I see no reasonable chance of success in 1 weeks time.

#### thingmaker3

Joined May 16, 2005
5,083
LED and sensor will work. Here is a divide-by-n counter: http://www.wenzel.com/pdffiles/161divdr.pdf

You should be able to breadboard this and get the bugs out in an hour or two.

Making a marketable version would of course take more than a week, as Papabravo has opined.

#### karthiksrao

Joined Oct 21, 2006
3
I'm not looking to build a marketable version.. its just a simple model..

I have a few ideas.. I thought if we could use a phototransistor so that when light falls on the transistor from the LED, it will start conducting and voltage across it falls to 0 (logic 0) and when ther's no light falling on it.. voltage accross it will be Vcc ..(logic 1).. i thought of tapping these pulse voltages so as to feed it into a counter...can this be done??

If it can be done , what are the components that will go into making the interface between the transistor and the counter?

also.. I thought the counters are readily available in the market..Is it so.. ? or do we have to build the counter...

#### BobJoe

Joined Oct 7, 2006
16
2 8-bit ripple counters. have the input of one by a push button set up for the operator (call this C1) and a light sensitive resistor as input (must go through a NOT first) for the other ripple counter (C2). have each appropriate output connected by NAND gates. have a single wire connecting each NAND gate so as long as one has a value of logical 1 then your conveyor belt will turn. when C2 has counted up to the same logical value as preset my user on C1 all NAND gates will read logical 0. the output is then fed into a transistor which in turn switches off the conveyor belt.

sorry i mostly came up with this on the fly and have no actual electrical experience so i dont know if this will work. also my appoligies if im not supposed to put logical in front of my 1's and 0's. the only problem that you may encounter is that the last object to go down the conveyor belt will just enter the the beam of the light for the resistor causing it to stop right there, you may want to tell it to count one extra to account for this.

im curious though, will this work? or is there major flaw in it?
BobJoe

#### thingmaker3

Joined May 16, 2005
5,083
If it can be done , what are the components that will go into making the interface between the transistor and the counter?
Any old buffer would do.

also.. I thought the counters are readily available in the market..Is it so.. ? or do we have to build the counter...
There are indeed monolithic divide-by-n counters available. Examples include the HCF4018B, the CD4059A, or the CD4018B. I don't know if one could be obtained quickly. The 74160 and 74161 should be readily available at many local supply houses.

#### Søren

Joined Sep 2, 2006
472
Hi,

I have a few ideas.. [...] also.. I thought the counters are readily available in the market..Is it so.. ? or do we have to build the counter...