Led display Digital Voltmeter question

[JacintChapo]

Hi!

Today I pieced together this V meter, and what can I say, it works verry well.  

[billy]

Did you make it on a breadboard using the schematic or just
build the PCB at once ?

[maestrodamuz]

I have checked out those inconsistensies and I have prepared the corrections, you guys will get them soon.

[maestrodamuz]

I have done serious work on the volt meter, I have really had problems getting a -5v supply out of a 9v battery. I tried using the replacement for the cd4009 as indicated in the data sheet from intersil, cd 4049 all to no avail. I actually wanetd to run the unit from a 9v battery for portability sake, now i have had to revert to the good old transformer and using an LM 317T and LM 7905 in conjuction wit 2 polar capacitors of differnt capacitances I have been able to get  the 2 voltages (-5v and +5v) now my problem is calibration, am using a 1k instead of a 1.2k to get the 0-2000v scale,(That is the only scale am using) I shall find out 2 nite if it will work.  

[MP]

Here is a circuit that might help with the negative supply. Easy to find parts. You might have to tweak the values a little for your application.

MP

[Gustavo Kowalski]

By the way, there are some differences between the scheme and the PCB photo-layout

Is P1 a TrimPot, like the scheme says, or a Trimmer, as the photo and article describes?
Is the ICL34 pin correct in the scheme? Going out to the Display?
Where are the C6 and C7 on the scheme? They are not there, just in the PCB layout you can find and try to discover...

Finally, if someone corrected the scheme, I would apreciate to see it.

p.s.: I tryed to assembly it on the ProtoBoard (breadboard?).

Thanks very much,
Regards.
Gustavo Kowalski

[MP]

Gustavo, if you scroll up to page 1 of this thread, Billy has posted some corrections to the circuit. I have also found a board layout file with schematic both in Eagle format on the Eagle site that uses these parts and is very similar. It was donated by a user. If you do not have the Eagle Layout program, you can get a free version from their website at the same time.
 http://www.cadsoftusa.com/freeware.htm

Billy: did you find any other corrections needed after your previous post?

MP

[Gustavo Kowalski]

Hello! Thanks for you reply.
I read Billy´s corrections, but I still do not know if its a TrimPot or a Trimmer, and I don´t know where the C6 and C7 goes.
It would be nice to make the corrections on the main site of the project, because I linked that site to many friends that looked for this circuit.

I´m getting this program you said, but where can I found the schematic? Thanks again and contratulations for the great site!

Regards.

[maestrodamuz]

Having gone through the circuits, datasheets, replacement guides (ECG master replacement guide from Philips) and after the alarm about the inconsistencies I came out with these corrections and I believe they are correct as far as am concerned. Also I have included a modified circuit diagram for the DVM which can measure both ac and dc voltages. The maximum ac voltage that can be measured depends on the type of rectifier used; I recommend an IC rectifier which has a peak reverse voltage of 1000V and maximum forward current greater than 3A.So as not blow up the rectifier leave a safe limit of about 100V i.e for a rectifier of PRV of 1000 V don

[mixos]

Hello Gusk4x4

If you use the PCB, this voltmeter will work very nice. There are some errors at the schem and maestrodamuz has poster here the corrections along with some modifications to measure AC exept from DC voltages:

http://www.electronics-lab.com/forum/index.php?board=4;action=display;threadid=353&start=0

Hope this clarify things

[blacksheep]

Does somebody know how i can make a digital amperemeter? It's for a power supply...

[Ani]

I tried to build the L.D.D.V. yesterday, using a breadboard and
I came up with peculiar readings on the LEDs.   I had followed the
schematic from smartkit.

I thought that I had a false ICL7107 and I dismounted the
components.  

Today I thought to check the data sheets of ICL7107 and MAN6960 in order to cross-check the connections. Found inconsistencies in the
article schematic !  

For example for the 1's display :

Article : ICL(6) -> MAN(10)
Should be : ICL(6) -> MAN(9)

another example :

Article : ICL(34)
Should be ICL(25) -> MAN(1) and so on... there are many there.

Moreover, the R1 should be 100K, not 180K, I refer to the datasheet
and the "Digital Voltmeter" project

Finally, the LCD dot, is pin number 5, emitted in the schematic.

I am about to search all the errors now and report back later,
after I will rebuild the voltmeter.

I attach the data sheets for further reference.  

Hi Billy,

After comparing the schematic with ICL7107 datasheet, I also realized those problems which are already mentioned by you.

If you have rectified those errors, and have drawn proper schematic, please put it on or mail it to me. I want to use it in my lab PSU.

Regards,

Ani

[mixos]

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:

[MP]

Here is a schematic and board layout that was donated by someone to the Eagle site. It is free to use. It looks like the project, but might be a little different. If you have the free version of the eagle, you can view it or even edit it to be what you want. If you do not have the free version of Eagle, go to http://www.cadsoftusa.com/ and download it.