Let's Make Robots!

DC motor test


Just wanted to know, if any of you know a good way to test DC motors?

I need to test my motors for: Max and min. speed, current with no load, current with heavy load and stall current.

When i measure the motors resistor, i get about 3ohm. Then i tried to calculate 4.5V / 3 = 1.5Amp. But if i am correct hose motors have a stall current on about 2.7Amp. Did i calculate it wrong?

The 2 motors i need to test, are those from the LMR Mr. Basic.

Not sure how to do those test.

Pic16F876a output


I have now looked trough my datasheet over 16F876A and cant find any info about how much voltage it will have when high out on etc port C, and how much current there will be.

Any1 know wich page to find that, getting anoing that i cant find it.

Calculations Formulars

Now it have been about 7years since i last worked with electronics at home, and i am now facing a realy big problem.

Over those years i have lost all my formulars to calculate diferent transistor koblings(Ub, Ib and so on), resistors, voltage, amplyfing, amp.

Any1 got those, and if so, can i then persuade you to either mail them to me, or post them in here? :0)

Code problems


I am using the LMR Mr. Basic robot chassie and motors.

I have now tried to write a program using aseambler code. It is for a PIC16F876A IC. My program involve the use of the A/D converter, and the PWM (Both PWM outputs) I want my robot to be able to slow down when its IR sensor (sharp) detects someting at about 20cm away from it. And i want it to stop when someting is about 10cm away form it, and then drive in reverse.

(Later i want it to be able to turn, but will have to wait)

speed and max frekvens


Is there any way to see what my motor controllers max pwm frekvens is?

And to masuere the speed on my motor?

I am using 2 normal 4.5V DC motors, the ones from LMR Mr. Basic



different motor controllers


I am wondering if any know how many different metodes there are to build a motor controller.

Right now, the only ones i know is : H-bridge with transistors, H-bridge with relays, different sort of motor driver ic

Any1 know more metodes, that can be used, and if you do, please post with link to a place where i can read about it.

Or if you already know there +sides and -sides, please write it.


how to setup a PIC for A/D and PWM?


After some tries, i realy got some problems with making my PIC 16F876A working right.

I need it to be able to A/D konvert 3 analog inputs, 1 where it need to be able measure lenght (10-30cm), and the 2 others it only need to be able to see if there is someting or not. For detection objects.

I also need to use the 2 PWM outputs, where it shall be able to switch between speeds (slow and fast) Think i got the PWM to work on a 16F628.

Couting on using an ekstern 20Mhz crystal.

From PIC 16F628 and PIC16F876 to PIC16F876A


I where using a PIC16F628 when i where making som experiment with PWM, but i need 2 PWM output. So i deciede to get a PIC16F876, but by mistake i got a PIC16F876A, now i got some very big problems, cant figure out how to set _config.

My other problem, is that i also have some tutorials with A/D converting for a PIC16F876, can i also use that code for a PIC16F876A, or is the _config different?

Motor controller and CPU problems


Just wanted to ask, if any had some good motor controller that also worked when they etc. put it together with a PIC or other mikro controllers. And if you have, if you would be so kind to post a schmatic of how the motor controller and CPU are connected :0)


In my projekt, the motors i am using can max handle about 4.5Vdc, and are dwaring about 2.5Amp when stall.

Do you all use a opto-cobler between the "brain" and the motor controller?

Motor and putting it together


My problem is that when i am running the motor controller with my motors, it work fine. And when i am testing my pic16F876 with my IR sensor that also work great.

Then come the problem, when i put it together it wont work. Also it wont work when i am using 2 different power supplys.

Can it be that the motors are to cheap, and are making to much noise, and pulling the rest dowm? If not any got some ideas what it can be?