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Author Topic: ICL7135 Voltmeter Problem, Help ??  (Read 3533 times)
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xpress_embedo
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« on: February 16, 2013, 03:33:04 03:33 »

I am trying to simulate the ICL7135 to make a simple Voltmeter but it is not working,
Can any one explain me why this happens.

My Simulation doesn't start it giving an error.

I am not getting whats happening, even i am doing connections as per datasheet in proteus.

Can someone share this project on making a voltmeter using ICL7135 in proteus.

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ppa88
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« Reply #1 on: February 16, 2013, 03:21:20 15:21 »

Hi,
I think this error is because of the floating voltage source V1 in the circuit.
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robotai
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« Reply #2 on: February 16, 2013, 03:27:46 15:27 »

Seems something missed. How about attach your DSN file?
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« Reply #3 on: February 16, 2013, 03:40:24 15:40 »

Hello!! ppa88

When i remove my voltage source the simulation starts running, i used generator mode in proteus to provide 120 Hz clock to the Clock in Pin and the simulation is displaying 0,0,0,0 on seven segment display but the switching between the Seven Segment is clearly visible.

Please tell me which voltage source to attach, even i attach a battery it stops working
 Sad

But no doubt i am one step ahead.


robotai

I had already attached my design file, please check the Proteus Design.text file to download that.
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ppa88
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« Reply #4 on: February 16, 2013, 03:44:47 15:44 »

I have attached the modified design.
Note the following points :
1. I have grounded the INLO pin although I am not sure whether it is recommended in a practical design.
2. I changed the clock frequency to 120 KHz.
3. The display corresponding to the MSD is missing in your design. You have to use the D5 output.
4. I have applied 1.32 volts and it is displaying 3199 since the MSD is missing

Best regards.
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« Reply #5 on: February 16, 2013, 03:59:36 15:59 »

3. The display corresponding to the MSD is missing in your design. You have to use the D5 output.

I didn't understand the meaning of this line
What is MSD

yes i intentionally didn't connect the 5th Seven Segment which is Connected by D5 Pin


And yes i is displaying 3199.

What is MSD, and it is displaying it very slowly.

Anyways i think i will work okay in practical hardware.



Posted on: February 16, 2013, 03:57:16 15:57 - Automerged

Okay i got it.

I must display 1.32V
and it is displaying 3199
as i had not connected the First Seven Segment

Did you checked the Datasheet of ICL7135
Page Number 9 that seven segment has plus symbol.


And pls tell me the meaning of MSD
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ppa88
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« Reply #6 on: February 16, 2013, 04:42:23 16:42 »

MSD stands for Most Significant Digit. For eg. the '1' in 1.3199 is the MSD.

Posted on: February 16, 2013, 04:00:58 16:00 - Automerged

With MSD added.
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« Reply #7 on: February 16, 2013, 04:44:20 16:44 »

I Connect one more Seven Segment Display.
Which must be operated to display the Most Significant Digit.

It is displaying the most significant bit also.

But as per datasheet of ICL7135 the MSD Seven Segment Transistor must be Connected with the Transistor which is also connected with the RBI pin of 7447.

When i connect this D5 pin to the 7447 IC transistor and the supply transistor of Seven Segment Displaying the MSD, proteus simulation fails.
Removing that connection is working.

Can anyone tell me how to display points
Means 1.399
How to display point.

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robotai
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« Reply #8 on: February 16, 2013, 06:11:47 18:11 »

The dot is always set right below MSD when using reference 1.0v.
Be aware that only 2 segments are connected on MSD to display "1", not all 7 segments. So you can still set dot and even "minus" on the MSD.
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« Reply #9 on: February 16, 2013, 06:16:13 18:16 »

Can you please tell me how to do so.

How to put a dot on Seven Segment.
As the Seven Segment i am using is not having dot in it.
And the one which has 8 lines, which my 7447 is just having 7, so even then i cant display the dot.
And how to display positive and negative symbol.

What does that 1.0V reference means, you mean to say that i can't measure 10V when setting 1.0V as reference.

As i am not able to measure that, that why i am asking that.
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robotai
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« Reply #10 on: February 16, 2013, 07:35:49 19:35 »

Refer to attachment. You need other component with dot on 7-segment LED.

To measure 10v, you would need to use 2 resisters to divide the input by 10 (said 9k+1k). So the input to ICL7135 would become 1.0v.
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« Reply #11 on: February 17, 2013, 07:04:31 07:04 »

Thanks It Helps...
And one thing more..

The POL pin here is used to Display the Polarity of Voltage, i didn't require the polarity that's why removing it.

Now i connected the D5 pin to Transistor Q1 as shown in Datasheet, i think this is used to Display Zero on the first Seven Segment.
As when RBI pin is High and ABCD pins are low Zero is Displayed.

But i am not getting zero on the Seven Segment.
Can you tell me why it is so.
In my Design Below the Voltage is 0.2397

Even then i am getting 1.2397 means in case '1' will be der, how to correct that.
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« Reply #12 on: February 17, 2013, 08:09:15 08:09 »

Sorry, I suppose you only need 1 without 0. To make MSD display 1 and 0 properly, you need to connect 7-segment of MSD from a-f. Current DSN only connect b and c. That's the reason why only 1 displayed but not 0.
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« Reply #13 on: February 17, 2013, 08:25:58 08:25 »

Thanks for your reply..
 Smiley
I just forget that, i must connect all the pins to display all the Values.

Actually i have to measure voltage from 0V to 30V, and upto one decimal point.

I am using 5 Seven Segment, i will display decimal in 3rd Seven Segment.

I will upload my pcb design and everything after i complete this.

I want to ask something.
I have a make a voltage divider at the input to sense voltage up-to 30V
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ppa88
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« Reply #14 on: February 17, 2013, 04:05:03 16:05 »

With polarity and dot to measure from -30V to +30V (Not tested fully.). You will have to use a voltage divider (divide by 10) to scale the input voltage to +/- 3 volts.

On my laptop it takes some time to stabilise.

Best regards.



Posted on: February 17, 2013, 03:54:29 15:54 - Automerged

Hello,
This will not work for voltages > 20 volts. Some more work is required.
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« Reply #15 on: February 17, 2013, 04:16:48 16:16 »

You are right..
It is not working when voltage is greater than > 1.999V and also not works when voltage it is less than -1.999V

Means the display range is (-1.99V to +1.99V)

 Cry Undecided
Why this happens...

I didn't get that why this happens???

In Datasheet it is written that 4 1/2 Digits.
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ppa88
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« Reply #16 on: February 17, 2013, 04:34:16 16:34 »

Looks like a limitation of the IC itself. It is 41/2 digit(19999 shown on page 2 of manual)
Page 9 of manual mentions +/- 2.000 V full scale.

Posted on: February 17, 2013, 04:29:56 16:29 - Automerged

A DMM will show  1.9999V ok but a 2V input will be displayed as 2.000 i.e. it will loose one digit . The IC is not capable of doing this on its own
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« Reply #17 on: February 17, 2013, 04:42:58 16:42 »

Its okay,
I will make the real hardware of this and post it over here along with the PCB Design.
Hope it will work properly in Real Hardware
And yes it looks like the limitation of IC itself.

Thanks for your help...
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« Reply #18 on: March 23, 2013, 05:24:33 05:24 »

i had made the circuit and its working without any problem.

on the input side i made a voltage divider which scale down voltage by 10
means 20is scaled down to 2v as ic can measure only 2v

by this i had made it to work for 0-20v range

but i had to do it for 48v range
can any one tell me how can i do this and if not 48 V then 30 v is also okay for me.

is it possible with this ic.
pls suggest something.
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« Reply #19 on: March 23, 2013, 06:03:29 06:03 »

When using 5 digit display it can show -19999 to +19999 and decimal point can be placed in front of any digit. Measurement results can be from .19999 up to 19999. This means that you can make only 0.2V, 2V, 20V, 200V, 2000V, ... voltmeters. For measuring 48V you must use voltage divider that suits for 200V measuring range.
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« Reply #20 on: March 23, 2013, 06:50:23 06:50 »

Yes exactly.
But that is not working

I used a voltage divider made by using 100K and 1K Resistors but that is not working properly.

31V is displayed as 26V and this is a huge difference.
Don't know why!!

And 31V is scaled to around 0.0297V when measured by multimeter.

I am providing clock using 555 IC which is providing clock of around 96Khz
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« Reply #21 on: March 23, 2013, 09:04:09 09:04 »

Hi,

It looks like your reference voltage needs adjustment.

Look at datasheet.

Good Luck.
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« Reply #22 on: March 23, 2013, 12:22:46 12:22 »

maybe you are right

but how can i give sharp 1v to the reference pin

i used a 10k resistor and 10k pot to scale down the variation of 5v to 2.5v and then rotate the pot
to give 1v to the ic
but sometimes the value gets changed
:-(

i think i have to use that 1.2v zener diode ic
but that is too 1.2v

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PaulC
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information is free and should be shared for free


« Reply #23 on: March 23, 2013, 10:41:08 22:41 »

1.0 V Precision Low Noise. Shunt Voltage Reference. ADR510. Rev. B. Information furnished by Analog Devices is believed to be accurate and reliable

Designed for space critical applications, the ADR510 is a low voltage (1.000 V), precision shunt-mode voltage reference in an ultracompact (3 mm — 3 mm) SOT-23-3 package. The ADR510 features low...
Features
Precision 1.000 V voltage reference Ultracompact 3 mm — 3 mm SOT-23 package No external capacitor required Low output noise: 4 μV p-p (0.1 Hz to 10 Hz) Initial accuracy: ±0.35% maximum Temperature coefficient: 70 ppm/°C maximum Operating current range: 100 μA to 10 mA Output impedance: 0.3 Ω maximum Temperature range: ?40°C to +85°C
« Last Edit: March 23, 2013, 10:45:47 22:45 by PaulC » Logged

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« Reply #24 on: March 24, 2013, 07:12:15 07:12 »

It is better to use 1.2V Shunt Voltage Reference ADR512W. It has lower temperature coeficient than ADR510 but higher initial inaccuracy which is +-0.67%. Higher ref. voltage makes possible needed corrections to set reference to 1V and/or to compensate errors in input voltage divider.
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