Led display Digital Voltmeter question

[MP1]

Sure. I just get tired of the scare tactics to newbies....you will fry this if you don't follow my instruction....etc.. but then I get emails from those who have built the originals with no problems, grumbling about what they feel is a false posting on this forum.

Projects Q/A is primarily for those who are actively building these projects. Not for theory statements or overall attempt at re-design in one's head. We have a forum for Theory discussions.
Thanks for your input.

MP

 

[MP1]

additional posts regarding theory discussion has been moved to the Theory forum.
We were getting a little off-subject here.
Thanks,

MP

 

[faizanbrohi]

Okay this is not a theory discusssion , i have built the ICL7107 voltmeter and is working great , form www.electronics-diy.com , here is the PCB layout and silkscreen. the lines are jumpers

These are the componenets list

VALUE        SHAPE        #    REFDES     

1.0MOhm_5%  R0204R7_5    1    R6         
1N4148      DIO_DO35    3    D1,D2,D3   
10K_LIN      TRIPOT10X5V  1    R2         
10kOhm_5%    R0204R7_5    1    R5         
10nF        MKHCON4A    1    C7         
10uF-POL    ELKO10R5    2    C1,C2       
15kOhm_5%    R0204R7_5    1    R3         
47kOhm_5%    R0204R7_5    1    R4         
100kOhm_5%  R0204R7_5    1    R1         
100nF        MKHCON4A    1    C4         
100pF        KERKO5X4R5  1    C3         
220nF        MKHCON4A    1    C6         
470nF        MKHCON4A    1    C5         
DIPSW4      DIPSW4H      1    JSW1       
ICL7107      DIP40S      1    U1         
ICL7660      DIP8        1    U2         
JUMPER      JUMPER      20  J1,J2,J3,J4,J5,J6,J7,J8,J9,J10,J11,J12,J13,J14,J15,J16,J17,J18,J19,J20
SEVEN_SEG_DECIMAL_COM_A 7SEG8DIP14B  4    U3,U4,U5,U6 
TEST_PT1    PB          4    GND,INneg,INpos,VCC

ICL7107.rar

 

[faizanbrohi]

The PCB artwork and layout , sorry for too many jumpers. but the thing is this panel meter was for something else then measuring voltage , i am actually calculating length from it . i will post the full project when it is complete

View attachment 39307

View attachment 39308

 

[gogo2520]

Hello

Someone was asking about the board that someone drewup in eagle. i looked at it and almost made it, went so far as to burn the board. I think that it isn't right. looks like the 7 segments are backwards.
Don't know has anybody eles tried it.  I'll post the files so you can look at em.
                                          gogo

ICL7107.zip

 

[MP1]

It's a double sided board. I think you are trying to mount them on the wrong side.

MP

 

[gogo2520]

Hello MP
    I know its a double sided board, what I think I did is burned it upside down.
  I think. I am doing heat transfers so I burned the printed the bottom and mirror the top and then printed. Don't know maybe I should of mirrored the bottom and not the top.  guess I will have to stare at it for awhile

                                          gogo

 

[MP1]

Don't stare at it too long....  ;D
As I understand it, the dots will start to connect.

MP

 

[gogo2520]

hahaha
      Ya MP thats what I think my problem was to begin with.
    Heres what I come up with. I mirrored the bottom layer and just printed the top.
  seems that works. I printed it out and played with it. Makes since that way.
      time to burn another board.
                      have fun gogo

 

[gogo2520]

AH BOO WHO :'(
    that way won't work either, makes the L7660 backards. I would use  the original project but Iwant to put a L7660 right board too.
              Oh well back to the drawing board.

Hey MP someware on this said there was a schmatic posted on the eagle web site, I coulde find it. You wouldn't  happen to have a copy of it  :
                            have fun gogo

 

[gogo2520]

Hello
                  MP the eagel pcb you posted don't work unless you drill holes throuth the 7107 to get the 7 segments to place right.    Thanks anyway
                                  back the the org.
                                      have fun gogo

 

[MP1]

Hey gogo,
Sorry for the late reply. I was on a business trip in Asia for the week and just got back this morning.
Here are the eagle files for both schematic and board. Feel free to make any changes you need. This zip has a parts list for the LEDs used in the design if you would like to use them. Otherwise, you might have to make changes to the schematic for the one you want to use. Also, you might be able to use one of the edit commands to just use a different package in the board layout.

MP

icl7107-7106.zip

 

[hungmao]

Hi,

I'm a newbie here. I just want to share some experience in doing this project since many problems encountered are very similar to other big brothers.
I have done this project with Smart Kit version and created the PCB with information in this webpage. Mine is configured in 20v DC range. In the very beginning, after I have finished, I found that the measured voltage cannot be locked with fluctuation of about 0.6v (my measured voltage should be regulated 4.5v, fluctuation range = 4.2v to 4.8v). I have measured the target voltage with another multimeter and confirmed that this voltage is stable. After the troubleshooting, I found that the following steps can help to mitigate the problems:

(1) flux residues must be clear after soldering.

(2) my voltmeter sourced by LT1085 regulated in +5v and attain -5v from ICL7660. But, my transformer's secondary output shared command ground with another power supply(9v-0-9v). The fluctation problem is mainly come from here. After separated the transformer, the fluctation solved in a great extent with only 0.05v (acceptable range for me).

(3) proper grounding and shielding for the voltmeter circuit.

Just my two cents. Hopefully these can help.

 

[MP1]

These are all good tips no matter what project you are working on. Thanks for sharing with everyone.

MP

 

[pier1]

yes
if ur taking the +ve voltage from the transformer o/p put a 1n4007 in reverse and the capacitor in reverse and then put a 7905 to get -ve voltag .

 

[vicious5id]

Hey wassup people! Man tonnes of work has gone into this circuit, I'm very impressed with all these radical ideas about thermometers and ammeter adaptations! Who'd have thought an IC first manufactured in 1977 (7106, 7107 is the sister IC) would still be so very useful today!

Anyway I just wanted to clear up a few things:

a) http://www.electronics-lab.com/projects/test/007/index.html
b) http://www.electronics-lab.com/projects/test/014/index.html

^ Are those two circuits exactly the same, if not do they accomplish the exact same thing?

I know that this project can be converted into an ammeter, I'd like to know if any of the above circuits (a & b) will measure current from 0 to 200 mA? Or better yet, 0 to 120 mA only. I have a circuit that supplies 0 to 120 mA to a 100 Ohm load and I want to know if this project can measure the current in the load to .1 decimal places perhaps.

Is it a simple case of using a 10 Ohm resistor for R3 according to circuit b? Will that give me a 0 - 200 mA display if I hooked this up as an ammeter?

Appreciate any replies.

v5 out.

 

[audioguru2]

Hi Vicious,
You want the current-measuring resistance to be as low as possible. You don't want to lose too much voltage across it nor ruin voltage regulation.

The IC is capable of providing a full-scale voltage of only 200mV but the Smart Kit version has 2.0V. Then if you use the Smart Kit version with a 10 ohm current-measuring resistor for 200mA full-scale, the circuit you are measuring will have up to a 2.0V loss and its voltage regulation will be terrible.

 

[vicious5id]

So you think that I should use circuit (a)?

Which circuit will give me the smallest amount of loss?

I understand that you need to measure the voltage across a small resistance to use a digital ammeter.

 

[audioguru2]

So you think that I should use circuit (a)?

Which circuit will give me the smallest amount of loss?

You should use the circuit in the datasheet. Circuit (a) is similar to it. It has a max of only a 200mV loss.

 

[MP1]

V5,
This thread was actually started from schematic (b). It is also the most common one used, since the LEDs are more common.
There is not a significant difference on these two projects other than the dual LEDs. They both get the same job done.  Schematic (b) should be a little more stable since it has a smoothing capacitor across the input. Other members have reported that schematic (a) shows some instability in displaying the numbers. Too sensitive without the cap.
Also, go back to reply # 26 in this discussion. This is where discussion of using this chip for an ammeter starts. You will most likely find some information there that will be helpful.
I highly recommend that you read all of the replies in this thread. I compiled three different conversations into one thread so that all of the discussions were in the same area.

MP