hello,

i need some help..I'm try to develop heart rate + noninvasive glucose monitoring by using Altera DE2 board..DE2 do not have a ADC..so i need to design my own ADC..how to choose an ADC chip? i prefer to use ADC0804 @ ADC0808..

someone can give any suggestions?

 

hello,

i need some help..I'm try to develop heart rate + noninvasive glucose monitoring by using Altera DE2 board..DE2 do not have a ADC..so i need to design my own ADC..how to choose an ADC chip? i prefer to use ADC0804 @ ADC0808..

someone can give any suggestions?

What's the resolution that you need? Would 16 bits be enough? Is your source signal differential or single-ended? Also, what's the source's voltage range? 0 to 5V? 0 to 1V?

 

i thing 16 bits will be enough..and not sure which one signal that i'll use..because i'm not rely understood about differential or single-ended..and my voltage range 0 to 5v..usually, the journal that i read..used ADC0808 anf ADC0804

 

i thing 16 bits will be enough..and not sure which one signal that i'll use..because i'm not rely understood about differential or single-ended..and my voltage range 0 to 5v..usually, the journal that i read..used ADC0808 anf ADC0804

Well, it seems that what you need is a single-ended ADC (though I strongly suggest you look up what a differential signal is... it's important for this topic)
I've used this chip in the past (among others) with those characteristics and I can tell you that it's easy to use, and very reliable... though soldering it to a PCB is a delicate operation... I burned three of those suckers before I realized that I had to lower my soldering station's temperature quite a bit so as not to spoil them. Also, you have to make at least 32 measurements and then average them to get a reasonable reading out of them. But they're very much worth it, I assure you.

 

There is good information on manufacturer's websites.
Here's an overview from Analog Devices (see section 6.9-how to choose a converter) and a list of application notes for healthcare products.
You could also try Linear Technology and TI-BurrBrown for info.
Microchip has lots of ADCs these days - pretty good for the price too.
Once you understand what you need, you can make a selection. Most of these guys offer low cost development/evaluation boards as well.
The 0804/0808 are pretty old parts with only 8 bit resolution. There are lots of cheaper/better/more bits/easier to use parts out there.
Good luck.

 

thank you for your information

 

There are some other things you should consider before starting your project.

• Part placement and trace routing on a PCB is critical when working with ADCs.
  
• Normally you'd need two power sources for your circuit, one would be a high precision, low-drift voltage reference (possibly bipolar) for the ADC and the rest of the analog parts, and the other would be used to feed the digital components. This way you would be minimizing noise and maximizing precision.
  
• Place all the analog components on one side of the board (left or right, not top and bottom) and the digital ones on the other side.
  
• A 4 layer board is preferable when working with ADC components.
  
• The ground on the ADC side of the board should be separate from the ground on the digital side, and they should both be joined at a single point as close as the power source as possible.

I have an extensive document describing all this somewhere in my files. I'll look it up later today and post it here when I find it.

 

Also keep in mind that ADC's come with a variety of interfaces. You can opt for a serial interface to save pins on the FPGA

 

Here's an excellent article describing some common-sense practices when designing ADC circuits.

 

thanks

 

i really have no idea what type of ADCs that should i use that can be interface with FPGA..because i don't have any experience working with Altera FPGA board..i need ADCs with more than 2 channel, 12 bits..and im using altera DE2 board..

 

i really have no idea what type of ADCs that should i use that can be interface with FPGA..because i don't have any experience working with Altera FPGA board..i need ADCs with more than 2 channel, 12 bits..and im using altera DE2 board..

How experienced are you with the altera DE2 board? Have you done any programming in it before? Or are you just getting started?

 

How experienced are you with the altera DE2 board? Have you done any programming in it before? Or are you just getting started?

i just getting started.. in 2 months

 

Then I suggest you first get thoroughly acquainted with the board before embarking in this little project... You have LOADS of studiying to do regarding serial protocol communications, data acquisition and display before you start working with an ADC... Do you have any previous experience with a different MCU?

 

i really have no idea what type of ADCs that should i use that can be interface with FPGA..because i don't have any experience working with Altera FPGA board..i need ADCs with more than 2 channel, 12 bits..and im using altera DE2 board..

ANY ADC can interface with ANY FPGA. Altera FPGA does not matter with choosing an ADC. What matters is you system requirements.

 

Then I suggest you first get thoroughly acquainted with the board before embarking in this little project... You have LOADS of studiying to do regarding serial protocol communications, data acquisition and display before you start working with an ADC... Do you have any previous experience with a different MCU?

yes..i hv previous experience with a different MCU...

 

yes..i hv previous experience with a different MCU...

What programming language did you use? Does this language have pre-programmed serial protocols in it? (CAN, SPI, UART, etc...)

 

ANY ADC can interface with ANY FPGA. Altera FPGA does not matter with choosing an ADC. What matters is you system requirements.

really? oh thanks ur make me fill more confident to do this project... now i try to used ADC0808..and from the journal that i read... most of the previous project used this kind of ADC...i hope it work nicely to me

 

What programming language did you use? Does this language have pre-programmed serial protocols in it? (CAN, SPI, UART, etc...)

assembly language..

 

Excellent

assembly language..

What MCU?