4553/4543 Counter Display

Thread Starter


Joined Sep 20, 2011
I am working on a project with a 339/laser sensor that will trigger a counter circuit suggested by SgtWookie using a 4553 and 4543. The sample circuit on the datasheet mentions the LED displays are low current with Ipeak < 10mA.

I am looking at 5" LED's from Futurlec.
DC Forward Current: 25mA
Pulse Forward Current: 150mA
Forward Voltage: 9.25V (11.00V MAX)

Would I just size the resistors accordingly or is there a better counter to use for larger displays? The purpose of this display is to "count" the number of "strikes" the kids get when the laser is blocked.

On a somewhat linked topic, I am wondering if I can copy the exact same circuit (once I get one figured out) and instead of using the sensor circuit to "count" strikes, I would use a 555 timer to make a simple 3 digit seconds clock. My original plan was to buy a simple digital clock display but I was a bit shocked at the asking price ($250) :eek:. I could use a standard stopwatch, but that is not very exciting and noone would be able to see the time. It would be a completely separate circuit/setup than my 339/sensor/counter setup.



Joined Nov 12, 2008
Hi CoachKalk,

I just purchased a couple of those 5" seven-segment displays from Futurelec and learned the specs posted are wrong. 9.25VDC is used if you need to drive the comma or decimal point. You need about 17.6VDC to drive any one of the seven segments. I don't recall for sure, but I think 20-25mA is still correct.

For the rest of my comments below, I assume you're following the circuit in the 4553 datasheet. If this is the case, be sure the display you get is CA (common anode) and not CC (common cathode).

Assuming you can use a wallwart rated about 19VDC or higher, you can use the 4553/4543 circuit with this 5" display if you place a ULN2803 between the output of the 4543 and the seven segment display. The resistors for the seven-segments go anywhere after the ULN2803 (on the output side of these chips). These will handle up to 50V and about 500mA per output pin. No need for additional parts.

You feed the 4543 into the ULN2803, connect the ground of the 2803 to the rest of the circuit and connect Vdd of the seven segments (at the collector inputs of the transistors) to 19VDC (probably a little higher). The resistors' value for the seven segments will depend on a few things.

In a nutshell, R_7_seg = [Vdd - (V_7_seg + V_drop_across_2803 + V_drop_ across_transistor)] / 20 (or 25)mA.

You can also make you own seven segment display nearly as big as you want for less money (but more time) by making it yourself using 5mm LEDs and plastic sheeting. I've made 9" displays using 5 LEDs per segment with a 12VDC supply. I can attach a picture here to give you an idea if you'd like.

Whether you use pre-made or decide to build your own display, you'll want to add a filter so you can see the display clearly. If you're going with red, get a red transparent sheet (0.010" thickness works well) or a 1/8" dark red acrylic sheet. You'll notice this if you have an alarm clock with an LED display.

Regarding the 3-digit seconds display, this circuit will work if you're okay counting up only (1, 2, 3). If you need to count down, then you'll want to use something else. Additionally, you'll need to add some circuitry to start your display at zero, not hard with the master reset, and the ability to pause/start if you want it to act like a stopwatch. I'm not sure how accurate a 555 will get you. I'd recommend Bill's 1-second clock which I'm using now for another project and works like a charm: http://forum.allaboutcircuits.com/showpost.php?p=374112&postcount=12.

Thread Starter


Joined Sep 20, 2011
I have looked over many of Bill's posts (not only the clock/time one you referenced) and have found them incredably helpful. I am very new to all of this and when I looked over Bill's 1-second setup, I immediately saw the seconds - minutes - hours mentioned and figured it was more than I needed. That could very well be my misunderstanding of what I was looking at though.

For what I am doing, it really could just be a 3 digit display counting up 1, 2, 3 etc... it wouldn't matter that 65 would really be 1 min 5 sec. Just a simple start button and stop button. I suppose a reset as well, like you mentioned. Make no mistake, eventually I would like to learn how to do an official stopwatch style circuit, but for now I need to recognize my limitations!:)

I would be very interested in seeing what you did to make your own displays. But, please be warned you would then open yourself up to my mind numbing, seemingly simple-minded questions if I would actually try it!

Thanks for your help.


Joined Nov 12, 2008
Ah yes, Bill's counter circuit threw me for a loop the first time he showed it to me. The key to understanding electronics, at least circuits anyways, is to look at one thing at time, understand it, then move to the adjoining thing. So, all you need from Bill's circuit is a one-second clock. All you need is the top half of his circuit, the CD4060 (and all the passive components connected to it: resistors, capacitors, crystal) and the CD4013. The 4013 is a dual D flip flop, meaning it has two flip flops, denoted U2a and U2b. We only need the one-second clock, so we don't need to use the second flip flop, so we can ignore U2b (we'll need to tie all the unused inputs to ground to eliminate any accidental triggering). Therefore, you're left with the circuit comprised of U1 and U2a. Not much to it (thankfully).

If I didn't love answering questions and explaining things, believe me, I and most of the people answering questions wouldn't be here. I'm still learning myself, but I love to pass on what I've learned and explaining it helps keep me sharp, so no worries - ask away!

I'll take some pictures tonight and post them tomorrow showing you how I made my own display and what a difference a filter makes.

We could certainly use Bill's full circuit and build a dedicated minute and second display, but it would require a much bigger circuit and many more chips as we'd need a pair of IC's for each digit (clock-to-BCD and BCD-to-7-segment), though we might save a few finding a dual BCD-to-7-segment IC or using only 2 displays of the 4553/4543 combo. All up to you, but I think you're right, starting out small and simple is best if you're starting out.

Thread Starter


Joined Sep 20, 2011
elec mech: Your explaination of Bill's circuits helps alot. Thank you. I do have a couple of questions still.

What/how do the c6,c7 and c8 capacitors impact the simplified circuit? It looks like a stand alone circuit so it may be obvious to an experienced pro that it links up to another location, but I just see it as "there", not linked to the other.

My next question is about the arrow/output labeled "Seconds Clock". Would that go to the LED displays? With this simplified circuit, would I still be able to have a 3 digit display fed from the circuit?



Joined Apr 11, 2010
C6, C7 and C8 are decoupling or bypass capacitors. They are required between Vcc and ground on the ICs used in the circuit (See this post for an explanation http://forum.allaboutcircuits.com/showthread.php?t=45583 ).

The fact that they look like a standalone circuit is just because they are shown in a schematic convention; it is implied that they are bypass capacitors for each of the ICs.

But good catch and an excellent question. Everyone doesn't know these conventions and it is good that you asked.


Joined Sep 26, 2009
Just kind of passing through, and thought I would put my 2 cents in for some other resources >> Here is a versatile 3 digit Up/Down counter http://forum.allaboutcircuits.com/attachment.php?attachmentid=21313&d=1279998991, I am sure with a little altering of the outputs, it would work with any size LED displays you may have, but may be good if you decide to use a count down type timer....

and here is another example, but using a PIC microcontroller to multiplex 4 digits using the same data outputs >>> http://forum.allaboutcircuits.com/attachment.php?attachmentid=18943&d=1272466284, this simplifies the electronic part but you will have to write code and program a uC,

the outputs of both could be transistor driven to handle higher current loads for larger LED displays.....


Joined Nov 12, 2008
Exactly what djsfantasi said . . . the link djsfantasi provided is a good one, and ditto - good eye!

I'm using the 4511 IC now with the 4510, similar to the circuit BMorse posted. Whether using these circuits or a microcontroller, you'll still need a transistor or MOSFET array to handle the higher voltage (and in some cases the higher current) of a larger 7-segment display. Note that most of the circuits shown using 7-segment displays are using those that are less than an inch tall which typically use small voltages and currents. For anything much bigger, you'll need something to act as an amplifier or higher-powered switch, hence the transistor array.

If you opt for an up or down counter, need to control each digit individually, and don't need to preset the display to anything other than 0, then the CD40110 works really well - it combines the function of two ICs into one. You don't need this for your current project, just giving you some other display ICs to consider in the future.

Thread Starter


Joined Sep 20, 2011
I have looked at several sites for ordering and I think I am ready to jump in and get parts. I have combined the circuit shown on the 4553 Datasheet (for my planned Strike Counter) and the BOM from Bill's 1-second counter circuit linked previously in this thread (for my seconds clock). I know I am missing some other more common parts, but I have many already and I hope Radio Shack will have other common components.

I have a few questions. I have MC14553B and MC14543B in my notes. Futurlec has the MC14553B, but only lists a CD14543. It does have a CD14553 as available also. I am not sure what the MC/CD references and I am not sure which combination would work together.

Also, I am looking at thr 5" LED 7-seg displays - currently listed @ 11.90 each. In the process of finding them again, I found a "Segment Display" listed @ 14.90. The desc. states driver transistors and step down resistors are all pre-installed and the display is suitable for standard IC Drivers. I am assuming the resistors that are installed limit the voltage source, but I am wondering if any of you have an opinion on displays like this. For an extra $3, it seems like several steps are already taken care of. Right?

Here is what I have so far. If you see any glaring screw-ups please let me know.
MC14553 3-Digit BCD Counter IC
CD4543 BCD to 7-segment Decoder
ULN2803A Hi-Volt Hi-Current Darl. Array
CD4060 14-stage Ripple-carry Binary
CD4013 Dual D flip-flop with set/reset
2N5060 SCR
32.768kHz Crystal
Large Photocell
12V Pulse Siren
"Single Hi-Red 5.0"" CA 7-Segment LED Display"
CD4553 3-digit BCD Counter


Joined Jul 17, 2007
While Futurlec may have good prices, I don't like their very slow shipping times. I ordered some parts from them a few years ago; my credit card was charged for the parts & shipping the same day, but it took over a month for the parts to arrive. Their customer service leaves much to be desired. I have read reports on here of people having to wait a couple of months for parts to be delivered. However, in some cases, Futurlec is the only place you can find certain parts.

If you can buy your parts from Digikey, Mouser, Avnet Express, or other authorized distributor, I'd strongly suggest going that route. You'll get your parts within days of ordering.

Darlington drivers: if you are going to be operating your CMOS circuit from 6v or more, use the ULN2804A instead of the ULN2803A; the difference is in the input base resistor. Whichever you use, you will need to look in the datasheet plots to see what the Vce(sat) will be prior to calculating the current limiting resistors for the LED display segments.

If each channel will be sinking up to 50mA, the Vce(sat) will be around 0.63v to 0.7v. Add that saturation voltage to the Vf of the 7-segment display before calculating the current limiting resistors.

Don't depend upon Radio Shack to have the other parts you need; you may be quite disappointed.
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Joined Mar 24, 2008
Why not add were you live to your profile CoachKalk? It can be helpful for people recommending sources.

Mouser has delivered to my house 3 times in less than 24 hours, it is because they are part of the Dallas metroplex. Still, very impressive.

I have found this thread quite interesting, especially the other counter/decoder chip options. Those tend to be handy circuits for a wide range of applications.


Joined Nov 12, 2008
I ordered from them a few weeks ago and it took a little over a week to get. This isn't to imply they'll adhere to this timeline, but it is the hope that companies get better over time otherwise they could go out of business.

Note that Futurelec ships from Hong Kong (the major reason for the delayed shipping) and will require someone signs for the package assuming you opt for the least expensive shipping method like I did. Unfortunately, I'm not home when the mail is delivered, so I had to go to the PO to pick up. If you're going to order from them, I'd suggest having it shipped to work since someone will be there to sign for it.

That said, I've attached a PDF showing pictures of the custom 9" display I did along with the 4" and 5" displays sold by Futurelec. The custom display is made from 1/8" thick, 12" x 12" gray sheet of PVC sold by McMaster for under $5 (not including shipping). The LEDs are from MPJA.com and are sold for $2 per 100. Not the greatest quality and you'll have to toss a few due to difference in brightness, but you can't beat $2! So, altogether, not factoring in shipping costs, the two-digit 9" display costs about $7. You can get bigger pieces of PVC and easily do a 3-digit display or bigger. To boot, it operates off of 12VDC.

Sgt. Wookie makes a good point, use the ULN2804. I haven't used these in a while - the 03 is designed for 5V operation while the 04 works off of 6-15VDC. Whatever display you opt to go with will require more than 5V and the other ICs should work with those higher voltages as well eliminating the need for a regulator (hopefully). I'd also suggest buying a few UDN2981 or UDN2982 ICs. These do the same thing as the 2804, but source current instead of sink it, which means they will work for common cathode displays. If you end up using the 4510/4511 or 40110 ICs, you'll need these instead of the 2804s. Futurelec sells the UDN2981 cheaper than most places I've found.

I'll look over your list and get back to you. I agree with SgtWookie, try to put together as complete a list of required parts for your project as possible and order as much as you can from whoever you place an order with. RadioShack, while I'll defend it some since I used to work there, cannot be relied upon to have that last component you need. To boot, if you're trying to save money, you'll pay a lot more. Futurelec sells resistors for 1 cent each! RadioShack will charge you 20 cents or more each and only in bundles of 5 or so. If you need one resistor, you'll spend over $1 to get it. I went through my resistor collection and ordered everything I was low on or missing for general inventory plus what I needed for my current project.

In my opinion, if you're ordering stuff anyway, stock up on the following if you're planning to get into electronics. These are always handy and allow you make due if you're missing a value in between by putting them in series or parallel. Plus, they won't cost you much. Maybe someone else can chime in if I'm missing something?

Resistors, 20 or more each:

0.01uF Ceramic, 20+
0.1uF Ceramic, 20+
1uF Electrolytic, 5-10
10uF Electrolytic, 5-10
100uF Electrolytic, 5-10

1N4148 or 1N914 or 1N918, 20+
1N4001-1N4007, 5+ (all models or just a few, the higher the last digit, the greater the voltage it can handle, 1N4001 and 1N4004 would be good)