Building a 7 segment LED display - Please help

SgtWookie

Joined Jul 17, 2007
22,221
The first LED is shown in the photo as a dual 7-segment display, but all HDSP-F series are single-digit displays; the HDSP-G
series are dual displays. They are also different dimensions:
HDSP-Fxxx 12.9mmH x 9.79mmW (0.51"x0.385")
HDSP-Gxxx 17.02mmH X 22.86mmW (0.67"x0.9")

Additionally, both of those displays are common anode. The board is wired for common cathode. This could be changed by reversing diodes D9 through D11, and changing the 4056 pin 6 DFI input from ground to Vdd.

Red LEDs typically have a Vf of 1.8; green has 2.1. This means different current limiting resistors could be necessary for the green displays.

The 220 Ohms for the DIP resistor and 180 Ohms for the two individual resistors were based on a Vdd of 5VDC, Vf(LED) of 1.8v and I(LED) of 15mA.
Rlimit = (Vdd - Vf(LED)) / I(LED)
Rlimit = (5 - 1.8) / 15mA
Rlimit = 3.2/0.015
Rlimit = 213.333... the closest standard value is 220.
Calculating actual current:
I(LED) = 3.2/220
I(LED) = 14.545... mA

The individual resistors are a special case, because there are diodes in the path that have a Vf drop of about 0.7.
This 0.7v drop must be subtracted from the supply voltage along with the Vf of the LED.
Rlimit = (Vdd - Vf(LED) - Vf(diode)) / I(LED)
Rlimit = (5 - 1.8 - 0.7) / 15mA
Rlimit = 2.5 / 0.015
Rlimit = 166.666... the closest standard value is 180.
Calculating actual current:
I(LED) = 2.5/180
I(LED) = 13.888... mA
You probably won't notice the difference in brightness. If you did, you could put a 3.8k resistor in parallel with the 180 Ohm resistors.

It seems to me that using two different colors of displays would make the panel look overly "busy".

It looks like the panel is about 1" or about 24mm high - what are the actual dimensions of the panel?

There is no point in proceeding if things are not going to fit.
 
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Thread Starter

Big KJ

Joined May 25, 2008
21
Hi SgtWookie,

Sorry for my mistake, the correct 7 segment commom leds cathode are:

http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=2465500

the green one and

http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=2465493http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=2465487

the red one.

They have (well I'm assuming this...) what looks a brighter Red version:

http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=2465487

If you believe that I should use the brighter one, please do let me know.

About the size of the panel, it is 40mm (1 rack unit), so I tryed to cut a square hole on the front panel and the size in height of the two 7 segment leds must not be over 35mm.

Having one 7 segment led on the top of the other (as on the attached drawing) makes it about 34mm heigh, which is quite confortable for me.
They must be really edge to edge on top of each other to achieve this.

Also if they're on a PCB, the PCB must not have more than 38mm height, so if using the IDC plugs the better way is to have one at each side of the 7 segment leds, if possible vertical orientated, please see attached drawing.

I do understand that doing it this way, it probably got to be on a double sided PCB, in order to have the IDC male plug orientated inwards.

If it is not possible for you to do it double sided (or if I'm wrong) I'll glue the two 7 segment enclosures together and will solder directly to its pins (I'll avoid that if possible).

The reason for the 2 diferent colors is only to get the things easier to operate.

Again, many, many thanks for your great help and explanation - I'm really learning and enjoining this! :)

Cheers from Portugal
 

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Thread Starter

Big KJ

Joined May 25, 2008
21
SgtWookie,

Just a tought, if you believe that it will be better to use separate 7 segment leds instead of using dual display it is ok with me.

I choosed the dual ones not by the size but because I tought (probably wrongly...) that it might be easier for the PCB drawing.

If you believe that at RS they have a smaller sized ones that works it would be even better, please, just let me know which ones shall I order.

To my understanding the following ones might be perfect (size is more than perfect - much better than the size of the dual ones):

http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=0589092A

http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=0451057


I say www.rs-components.co.uk , because it is very easy for me to buy from them.

At last, if using diferent colors (red and green) poses some problems, if necessary, I guess I could perfectly stay in only one color.

I'm sorry, but I'm really new on this :(

Again, many thanks.

Cheers from Portugal
 

SgtWookie

Joined Jul 17, 2007
22,221
Hi SgtWookie,

Sorry for my mistake, the correct 7 segment commom leds cathode are:

http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=2465500
That is an HDSP-Fxxx series, which is a single-digit 7-segment LED display.

That is ALSO an HDSP-Fxxx series, which is a single-digit 7-segment LED display!

the red one.

They have (well I'm assuming this...) what looks a brighter Red version:

http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=2465487
That is ALSO an HDSP-Fxxx series, which is a single-digit 7-segment LED display!!!!


If you believe that I should use the brighter one, please do let me know.
Unless you're using this thing outdoors, you don't need the high brightness version.
About the size of the panel, it is 40mm (1 rack unit), so I tried to cut a square hole on the front panel and the size in height of the two 7 segment leds must not be over 35mm.
OK, so 17.5mm each is your height limit.

Having one 7 segment led on the top of the other (as on the attached drawing) makes it about 34mm heigh, which is quite confortable for me.
They must be really edge to edge on top of each other to achieve this.
OK, so is your height limit 35mm or 34mm? :confused:

Also if they're on a PCB, the PCB must not have more than 38mm height, so if using the IDC plugs the better way is to have one at each side of the 7 segment leds, if possible vertical orientated, please see attached drawing.

I do understand that doing it this way, it probably got to be on a double sided PCB, in order to have the IDC male plug orientated inwards.

If it is not possible for you to do it double sided (or if I'm wrong) I'll glue the two 7 segment enclosures together and will solder directly to its pins (I'll avoid that if possible).

The reason for the 2 diferent colors is only to get the things easier to operate.

Again, many, many thanks for your great help and explanation - I'm really learning and enjoining this! :)

Cheers from Portugal
OK, so what is the REAL vertical limit? I'm guessing 17.5mm at this point.

The HDSP-Gxx3's would work, but they only stock ONE that's common cathode.

You COULD wire up three for common cathode, and three for common anode, but it would just make things easier to have everything the same. Besides, if you made a mistake and hooked up a mismatched pair of LED/driver boards, it wouldn't work at all.

HE Red 7 segment dual, HDSP-G203, common cathode
http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=2465588

Green 7 segment dual, HDSP-G501, common anode
http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=2465724

Make a choice.
 
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Thread Starter

Big KJ

Joined May 25, 2008
21
Sgt Wookie,

Sorry for the confusion.

The case is a 1 unit standard rack mount.
The front panel is a costum made (by me) piece of metal with 40 mm high.
Please see the attachement.
The cut hole for the 7 segments led can be up to 35 mm, but ideally should not be higher than 20 to 28 mm.

There will be 3 rectangular cut holes:
Each one (as in the attachment) will contain one top led display (counting from 1 to 12) for one rotary switch and one bottom led display (counting from 1 to 12) for other rotary switch.

Repeating this rectangular cut hole 3 times will allow the 6 led displays I do need for the 6 rotary switches.

My choice for the 7 segment led will be made under your orientation giving priority to:

1 - the less trouble maker for you
2 - the smallest size possible
3 - less prone to errors (when assembling)
4 - possibility of using 2 diferent colors (one for the top display and other for the bottom display)

If the smallest single ones I found at RS can be used, the cut hole shall be around 25,4mm (2 times 12,7 mm) which would be fantastic:

http://uk.rs-online.com/web/search/s...uct&R=0589092A

http://uk.rs-online.com/web/search/s...duct&R=0451057

I do not have the problem of a daylight work, only refered these because I tought their brightness (for the red ones) might equal the green ones (just a thought).

The confusion for the commom anode was my mistake, I pasted wrongly the link as I was looking for the commom cathode as you told (anyhow your choice would be mine).

Sorry for the trouble.
Many thanks

Cheers from Lisbon, Portugal :)
 

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SgtWookie

Joined Jul 17, 2007
22,221
So, I guess this is going to be a long-term project?
Red 7-segment LED, HDSP-7513 0.3in BP
http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=0589092A
This one, the red 7-segment that you specified, is out of stock, but they might get some towards the end of July.
There also is no manufacturer's datasheet available from that page.

They do appear to have SIX of the green 7-segment displays, but the link you posted didn't work; I fixed it.
http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=0451057
The remainder would be on backorder.

The dual displays would certainly be easier to route. However, I'm going to wait until you actually have some displays in hand that you know will fit. Otherwise, I'll be doing a lot of flailing on this end, which certainly isn't fair to me.

Before I'm going to do anything further on your project, you need to:
1) Have the seven segment displays in hand that you know will fit and that you want to use.
2) They should all be common anode or common cathode, but not mixed.
3) I will require the manufacturer's part number and manufacturer's datasheet in PDF format for the displays, so that the library model can be accurately generated for schematic capture and PCB layout.

If you want to get this project done, I suggest you select just ONE of the dual LED displays, and forget about using dual colors. Use something like a modified yin/yang symbol to indicate which knob goes to which display.


This is getting absurdly complicated for simply indicating what position is selected on a rotary dial.

You are not helping the process by failing to research things in a meticulous manner. This is three times in a row where items you have "researched" have proven to be incorrect or unavailable. One simply can't complete a project with missing or incorrect components.
 
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Thread Starter

Big KJ

Joined May 25, 2008
21
Hello SgtWookie,

Sorry for my silence but been working till today.
Anyhow last friday I ordered and just received today the 10mm dual 7 segment led displays.

I got:

6 x Red 7-segment LED, HDSP-F153 10mm (www.rs-components.co.uk part: 246-5493)

and

3 x Green 7-segment LED, HDSP-F503 10mm (www.rs-components.co.uk part: 246-5500)

Spec sheets are on: http://docs-europe.electrocomponents.com/webdocs/0025/0900766b80025c05.pdf

If possible for you, I'll use 3 red ones and 3 green ones (this is by far what I'd prefer); if not, I'll use only the red ones as I do got 6.

Sorry for all this mess. Many, many thanks for being so compreensive with this.

Cheers from Portugal
 

SgtWookie

Joined Jul 17, 2007
22,221
Have you taken them out of the package they were shipped to you in, and looked at them?

My guess is that you have not, because if they were truly HDSP-Fxxx series Seven Segment Displays, you would discover that they are single digit displays, and you do not have enough of the green displays on hand to complete the project. You have just enough of the red displays for three two-digit displays.

Here is a link to the datasheet for that series of displays:
http://docs-europe.electrocomponents.com/webdocs/0025/0900766b80025c05.pdf

I have attached excerpts of that datasheet. If you look at the part numbers that you ordered, then the chart, and then the size drawings the chart refers to, you will see that all of the F-series are single digit, and the G-series are two digits.

Now if the displays you received actually ARE two digits, then they are a different part number from what you ordered; the vendor has made an error in their cataloging of components. In this case, I need to know what is the exact part number that is on the side of the displays.

If the red displays are indeed HDSP-F153's, they will be ridiculously bright in comparison to the green displays. You will likely have to increase the size of the resistors to 470 or more Ohms to decrease the current; thus lowering their intensity.

I do not have any of these displays on hand, therefore I cannot give you an informed opinion on what resistance will balance the display intensities.
 

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Big KJ

Joined May 25, 2008
21
Hello Sgt Wookie,

I'm really pissed off :mad:.

Sorry for the mistake but when I ordered the 7 segment led display I choosed these by browsing the pictures that they have at their website.

For these displays I got, they have a picture of a dual display, and yes, again, you are absolutely correct as what I got was single displays :(

When I first replyed to you I did'nt had the box oppened yet.

Anyhow at my local store (I'm going there again tomorrow) they have a very cheap dual red display at a great size for me (I had these at my hands allready);
The drawback is there they have no idea what the hell they are...
They have the following text in one side:

LTD4606R-NB
935TAIWAN

They believe these to be a red multiplexed (as they have only 10 pins) dual display common anode.

Trying to google this reference did not bring me into any results :(.

Tomorrow I'll went there to see if I can get the pin out, case, size and some other information, if you do belive they might fit.

If not, well, I will get the ones that they have and will find a diferent solution for the front panel; they do have red dual commom cathode displays, only larger than what I wanted.

I know that I'm less than a roockie on this subject (my experience is only for the soldering part :() so I'm again asking to excuse me for all this mess and to thank you for your kind help.

Cheers from Portugal
 

SgtWookie

Joined Jul 17, 2007
22,221
I don't know why you ordered them. :confused: I'd stated SEVERAL times already in the thread (FOUR TIMES ON THIS PAGE) that the HDSP-Fxxx series were single digit displays.

Is it that you just aren't reading what I've been posting? I don't get it.

You have to be very observant, and pay attention to the details. If you do not, there will be little hope of completing this project successfully.

LTD-4606R-NB - it's my bet that this is a Lite-On display.

See if you can get a datasheet from the manufacturer.

I see little hope of this project reaching a successful conclusion. You don't pay attention to what I write. You order things that I've suggested won't work. There really is not much point in me following up on this thread.

I suggest you finish this project by yourself, since you seem to know better.
 
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Thread Starter

Big KJ

Joined May 25, 2008
21
SgtWookie,

This is the situation:
On my local electronics store I was able to find only two kind of dual digit displays:

LTD4606R-NB
and
HDSP-5521 (hp533 F-)

Both are commom anode. I took both with me (I know the people inthere, so I can change or not to buy, later on).

As I did not found any information googling over internet I took the measurements, layout and pin-out for the LTD4606R-NB. Please do find this on the attached pdfs.

If you believe I can use this one it would be perfect as they are smaller and there are less cabling (this is my guess about the cabling - I'm not sure).

If not, I figured out a diferent way to have the bigger ones on the panel, so, if needed, I can use the bigger ones.

I do got the HDSP-5521 (hp533 F-) (Red dual) but commom anode. Please do find the attached spec sheet for it. If they are most suitable I can use these.

If I need to forget about these commom anode I got, and have the dual commom cathode, there's no problem.

I just ask you for help pointing me to the correct ones at RS and I'll buy the ones you do believe to be the most suitable.

I forgot about the 2 colors, lets use only the red ones; you're right!

Sorry for the trouble, and believe me, all this mess is not because I want to impose something or playing clever: it's only because my knowledge on this subject just sucks :(

Again, many, many thanks for your understanding and helping me on this.

Cheers from Portugal
 

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SgtWookie

Joined Jul 17, 2007
22,221
Your measurements for the LTD4606R-NB were not terribly accurate.
The pin spacing is 2.54mm (0.1"), not 2.5mm.

The LTD4606R-NB display is designed to be used with multiplexing.
The HDSP-5521 display is a non-multiplexed display.
The design of the board is non-multiplexed. The HDSP-5521 will work with it. The LTD4606R-NB will not.

You are accumulating paperweights at a rapid pace.
 

Thread Starter

Big KJ

Joined May 25, 2008
21
SgtWookie,

Just brought the LTD4606R-NB because I tought it might be easier to wire it to the main PCB (less wires, I guessed).
I had some trouble doing the measurements as my eyes are not that good :(

Anyhow if the HDSP-5521 is good for your schematic, that would be great for me too!

Can we go ahead with it and can I, please, ask you to draw the final :) schematic and the PCB? I guess that some modifications got to be made to the last schematic and PCB you kindly did for me (please do correct me if I'm wrong).

I must stress all my gratitude for you help - without it I would never have it done. Many, many thanks!

Can't wait to have it done and send you a picture of these on the rack ;)

Cheers from Portugal
 

Thread Starter

Big KJ

Joined May 25, 2008
21
Sgt Wookie,

Sorry for my silence, but only today I received the goods.
I do have now all the components to proceed.
I got the 6 red dual 7 segment led display commom cathode: HDSP-5523.

My doubt:

Which voltage should I apply on these pins (on the main PCB)?
VD
VDD
VEE
VSS

Any chance you can draw the small PCB for each pair of HDSP-5523 one on the top of the other?

Sorry for the trouble. Many thanks for your help!
 

SgtWookie

Joined Jul 17, 2007
22,221
I redrew it for the HDSP-5521; that's what you said you could get.

So you actually have the HDSP-5523 now?

That is going to require yet another redraw. :rolleyes:

Before I do that, I want to see a photo of the part numbers of the LED displays that you actually have.

All of them.
 
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Thread Starter

Big KJ

Joined May 25, 2008
21
I got both now...
Which ones should I use? I can use one or the other (I can get money back from the ones not used).

If the current PCB (the one on page 2 of this very thread) is for the 5521, that's no problem as I do have these at hand.

I just did not figured out you did change the Main PCB for these... (from the schematics I could not figured it: lack of knowledge from me). Sorry.

What about the voltages?

VD=? ; VDD=? ; VEE=? ; VSS=?

Any chance you can design the smaller PCD for the displays? Many thanks!
 

bloguetronica

Joined Apr 27, 2007
1,453
...
This is the situation:
On my local electronics store I was able to find only two kind of dual digit displays:

LTD4606R-NB
and
HDSP-5521 (hp533 F-)

Both are commom anode. I took both with me (I know the people inthere, so I can change or not to buy, later on).
...
Are you in Lisbon or can you go to Lisbon? I could indicate you Minitron. They have single and dual 7-segment displays from Kingbright. They have common anode as well as common cathode. The displays they have are 20mm high. Each single display is about 12mm wide and the dual is about 25mm wide.

Dimofel also has a wide selection of displays. They have of various sizes too. However, they are more expensive and the quality is not very good.

To find Minitron, you should look for Rua de São José. The street is parallel to Avenida da Liberdade and perpendicular to Rua das Pretas and Largo da Anunciada. If you find Elevador do Lavra, you should turn left at the corner of Dataram and go up the street. The shop should be at your left, about at the point where the street starts descending, near a new building that has a garage and in front of a beautiful yellow building with green shaders.

Dimofel is located at Avenida da Liberdade. Rua das Pretas is just across the avenue.
 

SgtWookie

Joined Jul 17, 2007
22,221
I've already redrawn it for the 5521, as I'd said.

The schematic required a number of changes to change polarity of the LEDs.
I'm about to go out for a while, and don't have time to post it at the moment.

I will later on this evening. I'm on EST, which is GMT+6 hours.
 

SgtWookie

Joined Jul 17, 2007
22,221
OK, here's a start. Had a few minutes to at least export images of the schematic and the board.

I decided to just put both boards together. You'll need to cut them apart.

As far as power and ground; all you have to do is:
1) Connect your - supply to Vee or GND; they're touching, so they're shorted. Vss is supplied from Vee/GND via J6; a jumper.
2) Connect your + supply to Vdd. It's jumpered to the other connections such as VD2

I did not really want to use so many different supply symbols, but that is what the library models of the ICs required in order to route them on the board. Rather making changes to the libraries, I wound up adding jumpers.
 

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