Hi there !
I been not able to work on my robot for a long time for some reasons and also not on electro-tech, but finaly I have finished it but it has just one problem that output of L293D is just 50mA. I am attaching a schematic of my robo.
The LEDs connected to MCU pins ( in alternate polarity to the same pins ) are the input pins for L293D and the LDR sensor section is shown far right. I know that these LEDs connected directly to MCU drop volatage so I tried removing them but did'nt help. I connected LEDs just for indication that at least digital part is O.K. Please help me I selected this robot for my collage project and have to submit in a week !
I am using 12V adapter for power supply for testing and then will switch to +9V battery.
Yes it will clamp it and that's why I wrote that I tried with removing those LEDs but then even the current falls to 50mA, so I connected them back just to make sure that at least MCU is doing it's job, and that's why I add them in schematic actually they are not permanently soldered there so please ignore them, and the worst thing is that before I tried removing LEDs the current was at 160mA but that was not enough to carry the load of ROBOT ( the motors were moving ) so I tried removing the LEDs and then THIS HAPPEN JUST 50 mA
Sorry ! I also missed some of your post, I actually don't know the current ratings of motor but it reads 2200 rpm, 6V , motors are those bulky one used in cassette players. The adapter reads 9V,500mA but it actually gives 11.56 v at output so I take it as 12 V.I also have two small motors used in china made toys (just like shown here https://www.societyofrobots.com/actuators.shtml as DC motor ) as it is taken from a toy it doesn't have any ratings on it but the toy runs on a single 3V pencil cell. When I connect these motors every thing stops and have to restart the ROBOT but attaching some resistance in series makes the motor run but very slow ( resistor is of 47 ohm)
This is the situation now, connecting those tiny toy motors not those cassette player's
currents at output pins of L293D - 84.5mA(for both motors)
Voltage at output pins without connecting motors - 8.05V
Voltage at adapter with motors connected - 8.05V
currents through motors while connected - 83.5mA
hope this will help you to help me
By the way I don't get that how a motor that runs on three volts connected at the output of L293D and not to MCU can reset the micro controller, I mean we are connecting it to output and not to input and a motor is a passive device, it runs on 3V doesn't generate 3V
After posting above reply I just strike with weird problem, that adapter is not giving 11.50V when connected to ckt, while disconnected it works fine , though ckt also works fine with 9V battery. The adapter has an LED and it becomes very light when connected to ckt. I tried another 7805 but doesn't work. Is it possible that though voltage of adapter is O.K. it might not giving current (rated 500mA ) ?
Edit :
I tried it with just a 7805 on bread board but then even it didn't work, there must be a diode got fused in the bridge of adapter.
Hey ! that works but not so well, The motor runs really fast but only when the robot is on the black line as it gets off the line on either side the MCU and whole ckt gets hang ( every thing stops), I thought the back emf of motor might be the problem and attached 0.1uF capacitor across each motor but that did not solve the problem .
And Pradeep you have suggested the computer source but I have an ATX 2.03 that has 12V but 16A and 15 A, I tried that once before and had my ckt fused, How to use that ? Will a simple current divider do the job ?
Is that 9 squares I see. Congratulations, couldn't happen to a more deserving poster.
Mike.
I don't get that how that reduce the back emf, I don't understand how the back emf voltage get grounded with those diode.
I am not sure that the problem I have asked about in the last post is because of back emf or is it ?
By the way what you (Eric) and Mike are talking about ? I don't get it ?
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