Led display Digital Voltmeter question

[MP1]

I haven't found that to be true. I have samples from both manufacturers and in my bench tests have found both to be stable. In most cases where someone has complained, I have found it to be a board layout error or design error. Most problems are cured by reading the application notes and data sheets.

MP

 

[audioguru2]

MP,
Intersil also have an improved one, also with guaranteed stability like Maxim's. Which one did you try and are people complaining about Intersil's old original one?

View attachment 37304

 

[Amr Bekhit]

I'm using the ICL7107CPL from Intersil. Incidently, I bought a Texas Instruments version today and plugged it in and the same thing happened. I think what will be best is if I scrap my old circuit and build another one from scratch. I find that sometimes helps to get kinks out that I miss. I'm still willing to hear any advice on the subject!

--Amr

 

[MP1]

MP,
Intersil also have an improved one, also with guaranteed stability like Maxim's. Which one did you try and are people complaining about Intersil's old original one?

Actually, it was your comments in the past about the specs that caused me to get the Maxim sample and compare. I have always used the Intersil chip in the past since as a general rule Maxim is always more expensive. Unfortunately, I have not noticed any differences. The two ICs that I compared were Intersil from approximately 2 years ago and Maxim from a more recent sample.
Reference voltage and supply voltage are critical in any A/D converter. Problems in those two general areas are the most common cause of instability in LED or LCD readings when using an A/D converter of any kind.

MP

 

[Amr Bekhit]

Good news! I've just rebuilt the circuit using the Texas Instruments chip and breadboard and it works perfect! What's more, I replaced the TI chip for the Intersil one and it works just as well! I must have made some mistake in my PCB the first time. Anyway, I'm glad that's all sussed.

Thanks for all the comments and help everyone!

--Amr

 

[joselima]

I acquired ICL 7107SCPLZ, he will be that he goes to function legal, or does not go to give certain?

Debtor

José Fábio Silva
Paraiba/Brasil

 

[MP1]

Dear Jose,
Your post did not translate very good. Are you asking if this Integrated Circuit Chip, ICL7107SCPLZ is a direct replacement for the 7107 in the project on this wesite?

MP

 

[joselima]

I want to know if I can use IC ICL 7107SCPLZ in the place of ICL 7107CPL

Thank


José Fábio
John People- Brasil

 

[audioguru2]

Hi Jose,
Yes, you can use it.
The "S" indicates that its stability is improved.
The "Z" indicates that it is made without lead. ;D

View attachment 37521

 

[joselima]

Very obliged, I go to use then.

Fábio

 

[telcotech]

blacksheep: you can use this Voltemeter as ammeter also using the connections see below:

You connect the ammeter in series with the load and voltmeter in parallel with load. To take a current measure there must be a load connected

Also you can read this: http://www.electronics-lab.com/forum/attachments/Digital_Panel_Meter.pdf
explaining different connections and R calculations.

Or use this to measure current:

What if I wanted to measure resistance? Could this DVM be modified, if so how?

Thanks

 

[danwu]

Hi, After reading all the experts building their own voltmeter. (using the ICL7107)
I decide to make a try and follow all the intruction...BINGO ...It's works with accuracy ...BUT one problem, I can't adjust adjust to Zero setting (without any load), always read as minus 00.1/00.2 If I tune to zero the reading with load will not accurate.

Anybody know the faults of have the answer?

 

[MP1]

Let us know how much inaccuracy you are seeing. Please give some examples of different voltages measured.

MP

 

[danwu]

Hello MP

The different is about 5 to 5.5v short with tunning to zero, the last digit still flicking between one and zero, if witout flicking (zero is stable) is about 6v less

although I'm able to set zero, the minus sign is always appeared, but when loaded with current to read the voltage, the minus will go off,...any answer?

Dan

 

[MP1]

Here is an application note regarding this device. I think it will answer some of your questions and help you solve some others such as the negative sign, etc.

MP

ICL7106-7107-an023.pdf

 

[danwu]

Hi MP,
thanks for the attachment

I manage to solved the negative sign by grounding the pin 30 (also can be connected to pin 21). the minus sign goes off.

But still can't rectify the zero setting problem, anyway the VM works find and accurate when put on load,

 

[noorussaad85]

Hi dude,
I have created the exact model as shown by ur schematic on the PCB.
But the only problem i'm facing is while measuring the voltage.
For example ............it displays a value of 1.4V for 1V input.......
14.1V for a 10V input........
28.2V for a 20V input......and so on
Basically the original factor gets multiplied by a factor of root 2 and then its displayed........
i checked it for a no. of values........but the problem prevails.......

try to get me a solution..........as soon as possible........

--Noorussaad.

 

[MP1]

Did you use the modified circuit or the original which had some errors?
How is your reference voltage? Have you included all of the capacitors or deleted some thought to be unnecessary? Others have reported excellent results, so you will have to take a close look at what you have put together.

MP

 

[Gruber]

Hi.
i have several questions about the voltmeter.
I built it,but it has some problems.

1.When the input is empty,i.e. no voltage is monitored the circuit has random segment flashing + random flashing of the minus sign.This occurs in (average) same periods like 10sec pause then flashes,10sec pause and again.
Any idea what can the problem be ?
Parts that form the "logical" unit for measuring should be OK,except the R1 which is 180k as written in project page.No C6 and C7 are added.
The power voltages are not perfectly equal - like +5,03V and -5,04V with common ground.The power supply is not a synchronized  dual supply,it has two separate different voltages -the negative and the possitive.

2.When no voltage is monitored what should be written on display ?

3.If this voltmeter is build as an ampermeter can it be used to monitor the current usage of the same curcuit ? The output voltage is stable 5V. ( if i find the attach function will attach an image ).

4.Can this project be done with common cathode instead of common anode ? Or i should use some kind of inverting system for the display ?


I read the topic and found some usefull information about this project.Unfortunately the older links are not working and cant check the whole info aboit it.

The circuit is built in a pcb with many wholes on it (dont know the english name for it )- not the specific pcb on the page.
Using this project : http://www.electronics-lab.com/projects/test/014/index.html
the 7107 is intersil's  ICL7107CPL.The 7-segment displays are some kingbright's and the are different from the displays used in project's page,but schematics is done with modifications in display part to fit the 7seven segments.


And the main question of all :

5. Can someone confirm that the project is working with the circuit posted on the page withoud having to change anything on it (i.e. C6&C7,power supply,etc).
I am asking,because i could done the pcb wrong and have some problems because of that,but the problem (random display flashing) is confusing me - either i messed with the circuit or the 7107 is out of use...
There is no problem to make the same PCB as shown on site (and this topic too),but i need to be some kinda sure,that this project will work as voltmeter.The curcuit i've made so far is for testing only,i hoped it can work properly and then make a "good" PCB for use,but i have problems.

Thanks for reading my reply and i hope someone can help me about the problems i have.

 

[MP1]

Some corrections were posted and then I think I merged all the topics together. They should all be in this thread. That is most likely why some of the old links do not work. Have you read all of the previous posts? I have previously posted a schematic and board layout in eagle format. Others have made this work and have posted about the problems they encountered. I have not heard of the problem with a flashing display. The two missing capacitors are bypass caps for stability of the power supplies. You should add them. Dependent upon how much ripple you have in the power supply, adding the caps might correct the flashing problem.

MP