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Analog Signal Generator Design

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Kamillas

New Member
I want to design an Analog Signal (0 to 10V DC) Generator. I am new to circuit design. I need help to design and manufacture this device. It will be very helpful if you can point me in the right direction.

I tested this circuit with a Arduino Mega board and generated upto 5V, but the resolution is very low, only 255 steps.

Device Specifications:
Input Power: 24V DC or 230V AC
Output: 0 to 10V DC(Should be able vary from the 4 Digit 7 Segment LED)
Output Resolution: Atleast 12 Bits
Interface through four Buttons (Up, Down, Set, Reset)
 

Kamillas

New Member
Analog ? >12 bits ? >255 steps ? 4 digits ? 10V DC output ?

Hi Externet,

1. Analog?
This device is similar to potentiometer(Which upon turning a knob varies the resistance and changes the voltage). This device should generate voltage which would be set in the 7 Segment LED through the Buttons.

2. 12 bits ? 255 steps ?
The device with which I tested(Arduino Mega) has an output resolution of (8 Bits, Increments of 0.0196V). The output resolution of the D to A Converter which we are designing should be at-least 12 Bits (4096 Steps, Increments of 0.0024V).

3. 4 digits ?
This device should have a 4 digit Seven Segment Display to show the current set valve.

4. 10V DC output?
Yes. The output should be variable from 0 V to 10V.
 

alec_t

Well-Known Member
Most Helpful Member
What do you intend to use as the voltage reference for the D/A converter? It will need to be very accurate and stable.
 

Kamillas

New Member
What do you intend to use as the voltage reference for the D/A converter? It will need to be very accurate and stable.
There will be no voltage reference for the D/A converter. The microprocessor/micro-controller should generate the digital signals based on the input by the user through the 7 Segment LED display and Buttons.

The user presses the Up key or down key based on the current step count in the controller the controller increments or decrements the count(12 Bit: 0 to 4096). The count is then calculated as voltage and displayed in the 7 Segment LED. The user presses the set button and the count is sent to the D/A converter. The D/A should give 0V for 0 Count and 10V for 4096 Count.

This device is going to be used for a Heater Control System, as a control signal to Thyristor controller. This device will also act as a general purpose testing device.

I have attached a system overview file.
 

Attachments

Les Jones

Well-Known Member
Most Helpful Member
I don't understand why you say the output to the D/A converter is limited to 8 bits. If you do not have enough I/O port pins with the current way you drive the display, input buttons and the D/A converter you will have to use a microcontroller with more I/O pins or do some multiplexing on the display and input buttons. You could also consider using a display that only needs 2 bits of an I/O port such as I2C.

Les.
 

Kamillas

New Member
I don't understand why you say the output to the D/A converter is limited to 8 bits. If you do not have enough I/O port pins with the current way you drive the display, input buttons and the D/A converter you will have to use a microcontroller with more I/O pins or do some multiplexing on the display and input buttons. You could also consider using a display that only needs 2 bits of an I/O port such as I2C.

Les.
Arduino has inbuilt analog port and that output is limited to 8 bits.

Please forget about the Arduino. Please see the attachment in my previous reply and help me desi the circuit.

Ask me if you need any more details.
 

ronsimpson

Well-Known Member
Most Helpful Member
http://www.ti.com/lit/ds/symlink/dac8811.pdf
Data sheet of a "digital to analog converter" with 16 bit conversion. (64,000 steps)
You can talk to it with the Arduino.
There are many of this type of part.
The output of most of these is 0 to 5V or 0 to 3.3V or 0 to 2.5V.
If you can get a part like this and make a good 0 to 5V then a simple amplifier with a gain of 2 will give you the 0 to 10V you want.

MicroChip makes some 12 bit parts that I have used many times.
 

Dr_Doggy

Well-Known Member
mostly selection will be user choice the buttons/lcd , choosing a dac just ensure it meets your criteria, 12v, 4096 steps...ect
 

alec_t

Well-Known Member
Most Helpful Member

spec

Well-Known Member
Most Helpful Member
Hi Kamillas,

To implement Ron Simpsons's approach of post #10, just connect one of the 12 bit serial to DAC shields, linked below, to your Arduino I2C serial output.

Then connect an operational amplifier to the output from the DAC so that the operational amplifier amplifies the DAC output to provide the 0V to 10V that you want.

An OPA2192 (also linked below) would be a good choice as it has a high precision, rail-to-rail output (RRO) and also has a good output drive current (60mA). The OP2192 is a dual opamp, so just use one of the opamps in the package.

Then all you need to do is to write a bit of simple code to complete the job.:)

spec

DATASHEET
(1) I2C serial input AD shield: https://www.adafruit.com/product/935
(2) OPA2192: http://www.ti.com/lit/ds/symlink/opa192.pdf
 
Last edited:

Les Jones

Well-Known Member
Most Helpful Member
Hi Externet,
The OP wants a programable DC output I assume as a calibration source. Like you I thought at first he wanted a variable frequency source until I re read the post.

Les.
 

Les Jones

Well-Known Member
Most Helpful Member
Hi Externet,
When you asked the questions in post #2 I was thinking the same things as you. (Like how can you have a DC output on an AC signal generator.) In his answer in post #3 he says he needs at least 12 bits resolution. (Steps of 0.0024V) As this is so precise I assume it is some kind of voltage calibration standard rather than a bench power supply like the items that you have linked to. The microcontroller data entry and display is very simple to implement but I have not done any work with prescission D to A converters so I can't give any advice in that area.

spec,
Banggood.com have these DDS signal generators in kit form for between 8 and 9 pounds. I have been tempted to buy one of these in the past but the logical side of my brain won as I have a nice HP signal generator that goes from about 4 hZ to 2 Mhz

Les.
 

Kamillas

New Member
Hi All,

Happy New Year...

Sorry for not replying for the past two day. Thank you all for your suggestions.

I have ordered MCP4725 from this link. First I am going to generate 0 to 5V through this device. Once this setup is successful I will go for the 10V generation with Opamp. These components might reach me within the next couple of days.

I will post the progress...
 

spec

Well-Known Member
Most Helpful Member
Hi Kamillas,

and a happy new year to you to.

It will be interesting to hear how you get on with the I2C/DAC shield.:)

spec
 
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