ic uln2803 and 74ls164

hello,,, i had start to make a 8051 project of scrolling led display that uses IC ULN2803 and IC 74LS164 but i dont know anything of these ics ,,,, i had searched on google many times but i dont found anything important for me ,,, i had downloaded datasheet also but its not enough so please tell me some sites that contains whole information about these and almost all ics ,,,,, tell me something that contains start to end data of these ...... please help me i will be very grateful to u.....

thanks
dharmik

Interesting project. It is a little hard if you didn't have enough knowledge of digital circuit. I just searched about ULN2803 and 74LS164, use your 8051 connect to 74LS164 input, and the output of 74LS164 connect to ULN2803. Program a serial data output from 8051 to 74LS164. That's the brief structure. check the datasheet to config your chips. Give them right powered and grounded. And remember to add enough resistor that you won't burn the LEDs, most of them cannot handle voltage of 5v.

For website information. I like to use datasheet, for they have detailed parameters. And search the name of your chip not the ID. People might use similar chips to design same function circuit. You can learn from their circuits and design your own.

And I also suggest you try some SPICE software like PSpice (you can download a student version), and I also like Proteus (Labcenter Electronics) which gives you more chips for simulation ( check if you can use the demo version to simulate the 8051 chip).

thank you so much,,

The ULN2803 is basically an array of darlington transistors (i.e. a pair of transistors connected in the "darlington" arrangement). Plus the base resistor is supplied so all you have to do is connect the 'Q' outputs of the 74LS164 to the inputs of the ULN2803. The outputs are NPN "open collector" so they drive low. This means you must connect the LED to the positive supply via a resistor or common current source.. So, the cathod of the LED connects to the output of the ULN2803 and the anode connects to the positive rail via a current limiting device (such as a resistor).

FYI: if all you are driving are LEDs the ULN2803 might be overkill--unless these are high current LEDs. I mean, it will probably work, but for a 20ma (typical) drive current, a regular transistor [array] will suffice. Also, the required input voltage of the ULN2803 might be too high for your LS logic to drive if the LED current is very high. That's the trouble with Darlington Transistors, they have a higher input drive voltage, and they have a higher saturation voltage. Both could become problems in a high LED current design. A better solution might be logic level MOSFETs. BUT, if the LS device DOES have trouble driving the ULN2803, then add a pull up resistor to each of the 74LS164 outputs (probably around 2K). This will pull the voltage up to a level that WILL drive the ULN2803.

Also, try searching for "Application Notes" on each IC. Try a Google search and if that doesn't work, try going to the manufacturer website and see if they have application notes.

Use the 74hc164 – its more modern and available with better performance. These are available from TI, onsemi, Fairchild and NXP – likely more.
I Recommend the ULN2803A its available from TI and is pin compatible with most of the ULN2002, 2003,2004… all of these are on the TI website.
www.ti.com
Hope this helps