Need help in making our light following robot using NE555 IC's to work on a pcb

Thread Starter

YMSmash

Joined Oct 26, 2017
3
hello, ive been having trouble with our pcb layout for our light following robot. for some reason, only motor 2 works on the pcb layout, with motor 1 completely dead. here is the schematic diagram that we're trying to follow and the pcb layout we made:
schematic:

YMS_nl5kTlb.png
pcb layout:

YMS_pcb_Lkb3LG5.png

the jumper wire was an improvisation because originally we didnt put a connection between battery negative to IC 2's pin 1. we've rechecked the connections over and over but we feel like there's nothing wrong with them and couldnt see the mistake (if there is). it also couldn't have been our components since they were all newly-bought and tested. im assuming that maybe theres something wrong with the resistors, the jumper thing wasnt a good fix, or that maybe we didn't properly follow the schematic design.

can anyone point out our mistake here? i'd really appreciate it. thanks in advance!
 

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AlbertHall

Joined Jun 4, 2014
8,375
There should be a capacitor beween pins 2&6 and ground to set the '555 timing. Neither '555 has this capacitor fitted.

Are the LDRs intended to turn the motors on and off, or control their speed?
 

Thread Starter

YMSmash

Joined Oct 26, 2017
3
There should be a capacitor beween pins 2&6 and ground to set the '555 timing. Neither '555 has this capacitor fitted.

Are the LDRs intended to turn the motors on and off, or control their speed?
they were intended to turn the motors off

i tried putting a capacitor between pins 2 and 6, and while both the motors work now according to the simulation, i couldnt turn them off when i turn take off the light from the LDR

whats supposed to happen is that the motors are only runing when the LDR senses light (in which case it stops when it doesnt)
 
Last edited:

AlbertHall

Joined Jun 4, 2014
8,375
OK, remove R2 and R4 (and you won't need the capacitors now). You can adjust the light level at which it switches by changing the values of R1 and R3 if necessary.
 

Thread Starter

YMSmash

Joined Oct 26, 2017
3
R2 and R4 based on the schematic right? that seemed to work just fine, but it was working just fine iin the simulator even with those resistors connected. could the 2 extra resistor that you said to remove be the reason why only 1 motor is working?
 

AlbertHall

Joined Jun 4, 2014
8,375
The original circuit is not a standard use of the '555. I don't know just what it would do in that arrangement. As it was being used in a way not intended by the manufacturer it may that some chips will work that way and some won't. The simulator has a mathematical model of the '555 which wouldn't be designed with that original configuration in mind so it may not follow just what the actual would do.
 
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