The $40 Line Follower Help

[Libraoct7]

Hi, I have a question about the $40 Line Follower circuit. In the picture you provided, you connected the joint of the two emitters of transistors to the track pin of the preset. But on the graphical diagram it show the connection of the joint of the two collectors of the transistor to the track pin of the preset. So, which one is correct?

[Soeren]

Hi, I have a question about the $40 Line Follower circuit. In the picture you provided, you connected the joint of the two emitters of transistors to the track pin of the preset. But on the graphical diagram it show the connection of the joint of the two collectors of the transistor to the track pin of the preset. So, which one is correct?

Is this the problem?


It is seen from above and the collectors are the ones with the red (positive) wire.
The blue wires goes to their basis pins and the black are on the emitters.
The left side collectors seems to be missing a wire to the positive side of the 100µF capacitor.

A quick glance at the photos does indeed seem to show a somewhat different layout.

I have nothing to do with this circuit, so I am not sure what the design thoughts about it were, so better hope Pratheek swings by and drops a comment on it (or try a polite request on his PM).

[Libraoct7]

 Thanks for your reply. I have waited for so long for someone to reply. I will try the PM Pratheek on this part. Thanks again. I hope you can answer my other questions on the other threads.

[Libraoct7]

I think you might be correct for using a NiMH or NiCad. I will try to buy one and try it, but before I more than one trip to the shop I need to know if the parts I have will do the job or should try to look for other parts. Here are the other parts I have:

1- I used L293NE instead of L293D. Does that matter?
2- I used 22k preset, instead of 20k preset. I could not find 20k preset. Is that OK?
3- I used 100uf 35v capacitor instead of 100uf 25v
4- I used BC548 PNP
5- I used 100rpm motors
6- I used a multimeter to check for any bad wiring and for the amount of voltage that is going into the motors.

[Libraoct7]

I have another question about the $40 Line Follower. In the picture it shows that you connected the collectors of the transistors using black wire, and connected the emitters of the transistors using red wire. But then you connected the joint of the collectors (black wire) with the track pin of the preset using red wire. So now the Black wire and the Red wire are connected. Is that true?

[Soeren]

Hi,

1- I used L293NE instead of L293D. Does that matter?

You have to provide some fast diodes to protect the outputs, the L293D (hence the suffix "D") has got them, the L293NE needs external diodes added (but can then supply almost twice the current of the "D" type).

2- I used 22k preset, instead of 20k preset. I could not find 20k preset. Is that OK?

Yes, it's fine.

3- I used 100uf 35v capacitor instead of 100uf 25v

OK. You can always use a higher voltage rating than specified, as it is just a measure for how high a voltage it can handle without breaking).

6- I used a multimeter to check for any bad wiring and for the amount of voltage that is going into the motors.

Telling us the voltages you measured over the motors  may be usefull info - telling us that you did measure them isn't.

[Libraoct7]

hmmm I am new to these terms "needs external diodes to be added". So are you saying that my L293NE will not make my robot work?!! And what do you mean that I need an external diodes to be added, and where and how to be added? I do appreciate your help and time in helping me. Thanks a lot.

[Admin]

hmmm I am new to these terms "needs external diodes to be added". So are you saying that my L293NE will not make my robot work?!! And what do you mean that I need an external diodes to be added, and where and how to be added?

Open up the datasheet for your new motor driver. You will find a schematic that shows diodes, and the locations that you need to solder them in.

6- I used a multimeter to check for any bad wiring and for the amount of voltage that is going into the motors.

and your results are?

[Libraoct7]

- I bought the motor driver in singles from the electronic shop near by. Datasheet is not provided with it. How do I get a datasheet for it? I went back to the shop and asked him for L293D, but he didn't have any. He said he will try to order it for me, might take 3 or 5 days to get them if he found any. But just in case he couldn't find any, I will try to use L239NE so I need to do some adjustment as you are imposing.

- when I used the multimeter to test the voltage coming out to the motor, the voltage was 0. I think that is because, as Soeren said to me on another thread, I was using 9v pp3 battery. I just bought a 9v NiMH battery with a charger. cost? about $8 for the battery and $16 for the charger. As I am writing this, the battery is being charged for almost 6 hours, 7 more hours to go.

[Admin]

I did a google search for L239NE . . . first two results is here at SoR, lol . . .

Anyway, you'll find it if you search for 'L239 datasheet'.

As I am writing this, the battery is being charged for almost 6 hours, 7 more hours to go.

sounds like a sucky charger . . . a good charger could do it in < 4 hours in slow charge mode

[Soeren]

Hi,

Datasheet is not provided with it. How do I get a datasheet for it?

Google

I think that is because, as Soeren said to me on another thread, I was using 9v pp3 battery. I just bought a 9v NiMH battery with a charger. cost? about $8 for the battery and $16 for the charger. As I am writing this, the battery is being charged for almost 6 hours, 7 more hours to go.

What I meant was that the PP3 form factor is too small - something like 6 AA NiMH-cells would be a much better choice, but a rechargeable PP3 at least have a lower internal resistance than the primary (non-rechargeable) battery equivalent.

[Libraoct7]

Hi thanks for your replies. I have finally found L293D. The motors are now running both of them. However, I tried to adjust the preset for line following. But, the red light never changes. I thought it was suppose to go dim or brighter, but it stays bright no matter how I turn or adjust the preset. What could be wrong?

[Aber]

hmm almost same problem. Look back to the replies in my thread you might find the answer to your problem.