[Savio]

The PWM method of motor speed control is one method but it can cause the motor to move in jerks.

You can use this if using a microcontroller to control the speed.

 

Reducing the voltage using a potentiometer will give a smoother movement.

[Savio]

Well my application requires that I constantly keep receiving data from a ADC and sending the converted values to the serial port. This operation should not be disturbed by anything like having to reload the timer.

 

I’m using the timer to drive a motor for a particular duration at a specified speed (the speed and distance can be changed by the user). This is for a surface roughness measurement machine.

 

The motor moves a arm with a gauge at one end along the surface of a material.

 

Your link to use the 8253/8254 was good, but i’ve already made the system using a second controller as a slave to do the counting. I had trouble interfacing the two AT89S52 in serial (I2C style) comm. but got them to work using one ENTIRE port to send data and two acknowledgement lines.

 

I will definitely try the method shown in your link. Thanks for the help.

[Savio]

ISIS Professional which is a part of Proteus will help you simulate your circuits, though you’d have to have a replacement for the ‘clap’ to be sensed by the microphone.

 

Like, proteus comes with a model for LDR. this can be replaced for the mic adjusting the intensity of the lamp in proteus would be similar to the intensity of the ‘clap’ falling on a microphone.

 

Good Luck!

[Savio]

Do you want the output of the OP-AMP to signal a ‘HIGH’ or ‘LOW’ to the microcontroller?

 

If yes, you can connect the output of the OP-AMP to the base of a transistor via a resistor and the collector of the transistor (also connected to 5V vcc) to your microcontroller. The transistor will then allow you to get 5V and GND on your microcontroller pin.

[Savio]

You could start with the first line with ‘0x80’ and count the characters being sent to the lcd. Once 16 characters have been sent, send the command to display from the second line – ‘0xC0’ .

 

and vice-versa.

[Savio]

Yeah, ISIS is only a simulator. You will need to export to ARES.

 

[Savio]

Which compiler are you using?

 

In Keil C51, ‘Target’ options will allow you to create a .hex file when compiling the code.

 

On the left side, right-click ‘Target’ and select ‘Target options’ —- then click ‘Output’ tab and tick’ create HEX file’.

[Savio]

I don’t understand – ‘circuit for 200 – 300 meter distance’.

 

Is that the lenght of the coil.

 

If its the transmission range that you want, it depends on the power you output. Selecting inductance and capacitance values only decide the frequency that you will be transmitting on.

 

Check out the book – Practical electronics for inventors by Paul Scherz.

Its got the stuff you need to know in designing a RF circuit.

[Savio]

Just wondering! won’t the zener be in breakdown condition  @ 8V causing red LED to be always lit up.

[Savio]

Well you’d require a microphone (condensor), a comparator and some other discrete components.

 

The microphone will output a voltage proportional to intensity of sound falling on it. This can be given to the comparator inverting teminal. A reference voltage to the non-inverting terminal will help ingnore any undesired operation. Create a voltage-divider for this terminal.

 

The comparator can then drive a transistor withwhich you can control another circuit you wish to add.

 

Play around with a circuit simulator, and create your own designs. Its more satisfying.

[Savio]

You could have the LDR interfaced with a comparator and the 555 configured in astable mode with a set frequency. The LDR can make the comparator output go high, when light falls on it, and power ‘on’ the 555 IC to outptut a square wave.

 

The LDR won’t detect the frequency of light though, only the intensity.

[Savio]

This formula is available.

 

L  = [d² n²] / [18d + 40l]

 

•      –    L  is the inductance in Micro Henries [µH]
•      –    d   is the diameter of the coil in inches.
•      –     l   is the length of the coil specified in inches.
•      –    n   is the number of turns.

 

wysiwyg_imageupload:8206:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

decide the diameter and lenght you wabt for your coil and accordingly calculate the no. of turns.

 

[Savio]

Regarding warning, you are missing a few function prototypes. Mention all the funtions used in your program before the ‘main()’ funtion. i.e. ” void display_lcd(unsigned char *str);”

 

Regarding error, this is a code which I usually use,

 

void display_lcd(unsigned char *str)

{

     while(*str!=0)

             {   

                  data_lcd(*str);

                  str++;

              }

}

 

Hope this helps, good Luck.

 

[Savio]

Hey Sanda,

Always refer the device datasheet to know the absolute maximum ratings.

For the AT89c51 MCU the maximum voltage on the VCC pin is 6.6V. But it is better to restrict it to only 5V. Use a 7805 IC if you want to use a 9V source.

[Savio]

Hey Parth,

 

It would be very helpfull if you could post your code with comments explaining the steps taken by you.

I assume you are using LCD in 4-bit mode. If so, initialize the LCD in 4-bit mode with command 0x02.

I have faced problems using KEIL while using ” #define LCD P0;”. Instead i’ve used “sfr P0=LCD;”.

 

Hope you solve your problem,

Regards.

[Author]

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