forder

How do I convert an analog signal to an 8-bit BCD signal? which component should i use?

also how do i do a multiplication to the number represented by the 8-bit BCD? what component should i use? i want to multiply the 8-bit BCD to a constant.

ericgibbs

You require a 8 bit ADC [analog to digital convertor], this will give a binary output, which you then have to convert to BCD.

The decimal value for 8 bits is 0 thru 255.

Depending upon what value your multiplier Constant is will determine which multiplication method is used.

We need more details.

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Eric
"Good enough is Perfect"

PIC tutorials:
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forder

well, i'm converting an analog signal (voltage difference), sent from a temperature sensor (thermocouple).. i need the signal to be in BCD so that i can display them on 7 segment.. i know that ordinary A/D converter only converts to binary.. like u mentioned, i need to convert them into BCD.. but i don't know how..

the second problem is that.. when i convert the analog signal, the resulting binary value represents the voltage difference from the sensor (am i right?), not the actual temperature value. so i figured that i need to have a constant that relates the voltage difference and the temperature, which then the constant can be multiplied to the voltage difference (in the form of BCD) so that the BCD represent the temperature value.

this is how i see and plan to tackle my project.. correct me if i'm wrong. any suggestions or hints are deeply appreciated.

JimB

I would approch the problem in one of two ways:

1 Use a micro processor such as a PIC. These have a built in ADC and can drive a display.
Any maths which need to be done on the digitised reading from the thermocouple can be done in the PIC.

2 Use an ADC such as an 7106 or 7107 (OK maybe they are ancient and obsolete, but bear with me guys).
These ADCs have a 0 to 200mV input range.
The output of the thermocouple will be a only few mV and so will need some amplification.
So, say you want the meter to read 100 degrees, set the gain of the TC amplifier to give 100mV when there is 100 degrees on the thermocouple.
Connect the output of the amplifier to the input of the ADC.
Job done!

However, are you really sure you want to use a thermocouple?
They have a low (mV) output, they also require cold junction compensation, otherwise they will just read the temperature difference above or below ambient temperature.

JimB

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Experience is directly proportional to the value of the equipment ruined.

forder

i'm required to use thermoucople. and also i'm not allowed to use micro controllers / micro processors.. so the only option i have is using IC's.

thank you for the amplification suggestion.. it does make sense.
so, after I convert the analog signal into binary, how should i convert the signal into BCD?

JimB

Look here:
http://www.maxim-ic.com/quick_view2.cfm/qv_pk/1353

and download the datasheet.

The 7106 and 7107 drive a display (seven segment LED or liquid crystal) directly, you dont need to mess about converting binary to bcd.

JimB

__________________
Experience is directly proportional to the value of the equipment ruined.