Using 8051 as a multimeter with 7seg LED display?

[Learner]

Hi guys,
I am looking to build a multi meter using 8051, I know that I can use an AD converter to display the voltage but what can I do to measure the resistance and the current?

Can anyone refer a link or suggest the easiest way to do this?

So far, I have figured that I can put the AD on the bus but would I need a HEX to decimal decoder on the bus to display the voltage? or shouldn't it be a binary to decimal decoder?

Thanks!

 

[williB]

to measure current use a one ohm resistor in series with the circuit you want to measure
since I = V/R
if R = 1 you are measuring current directly

 

[williB]

what a/d converter are u using ? some output strait binary others compliment the output .
u may or may not have to do some convertion in your 8051 program to get the output to straight binary , then u can use a binary to seven segment decoder..or you could do it all in the program by connecting the outputs of the 8051 directly to the segments of the display.

 

[Learner]

to measure current use a one ohm resistor in series with the circuit you want to measure
since I = V/R
if R = 1 you are measuring current directly

Hi williB,
That's an AWSOME idea!!!!! Thanks a million for that!!!!

no wonder I ain't getting straight As at college.......
why didn't I think of that! :?

 

[Learner]

what a/d converter are u using ? some output strait binary others compliment the output .
u may or may not have to do some convertion in your 8051 program to get the output to straight binary , then u can use a binary to seven segment decoder..or you could do it all in the program by connecting the outputs of the 8051 directly to the segments of the display.

Well, I am still trying to think my idea through and come up with a schematic.....

My goal is to make the 7 seg led be as spontaneous as possible with minimal circuit required, so I would not want to use an 8051 if it is not necessary.

So far, I am thinking of just using a 8 bit AD since I will be measuring less than 100V and then connect the 8 bit output straight to the binary to decimal decoder to the 3 digit 7 seg display. Any AD you would like to recommand, I think I will just pick some 8 bit AD from TI since they offer free samples

 

[Oznog]

You'll find an alphanumeric LCD display quite easy to drive, more visible in bright light, lower power, and far simpler to wire up. You sure you want an LED?

 

[williB]

well the TI TLV 1571 has ten bits resolution , parallel output
one lsb is 4.8 mV (nice) Vref is your supply voltage on this part(5V)

 

[williB]

You'll find an alphanumeric LCD display quite easy to drive, more visible in bright light, lower power, and far simpler to wire up. You sure you want an LED?

Is there any in particular that u have used?

 

[Nigel Goodwin]

You'll find an alphanumeric LCD display quite easy to drive, more visible in bright light, lower power, and far simpler to wire up. You sure you want an LED?

Is there any in particular that u have used?

Almost all LCD text modules use the Hitachi chip set, so as long as it's one of those it doesn't matter much one you use - I've used various different makes and models, you simple connnect it up and it works with the existing software (as it's written for the same chip set). The only difference I have found is in the contrast setting, you usually have to adjust that for different ones.

 

[williB]

so all i have to do is desolder the LCD from the other board and use it like that?
in the top photo is the 14 connections ? right?

 

[williB]

i just noticed that your photo (on you site ) of the LCD has 16 contacts??

 

[Nigel Goodwin]

so all i have to do is desolder the LCD from the other board and use it like that?
in the top photo is the 14 connections ? right?

Yes, that should be fine, I've used many LCD modules removed from other equipment.

The one in the photo in my tutorials has 16 connections because the other two are used for back lighting - which isn't actually fitted on the board in the picture, but some LCD's have the unused connections there anyway.

 

[williB]

thanks i 'll try it