24H 7-segment binary clock - Page 2 - Electronic Circuits Projects Diagrams Free

mike11298 · 12th August 2007, 08:32 AM

yes, true, but if you like, you might want to use a 4520 dual bcd counter. it has two counters in one, but it is very fiddly and particular about its values. Basicly its a big hassle.. BUT the good news for you is that they are ridiculously cheaper (mine was 60cents compared to a single BCD at $1.40) and, i have already used them in a seconds configuration for my clock i showed you. If the chips are availiable to you, you might want to consider it, I will give you more info if that is so.

spitfire · 12th August 2007, 01:39 PM

Yeh I actually found 2 4520's that I got from work in my component stash but they did seem alot more complicated for someone at my level in digital to setup for a 24H clock.

I emulated a seven segment display with 14 leds to test a 10 second counter and the number starts at 2...is this normal? or is it the 4000's series is slow to react and i need to place a cap somewhere to hold the clock pulse for a short period before it starts counting?

mike11298 · 13th August 2007, 10:43 AM

Are you using the 4510's? They should count (in binary) from zero to nine, then reset. If you need to reset earlier, you use an AND gate on the output pins to the input (in correct binary format for the number you want to reset at). Dont forget that even if you want an input to be zero or 0 logic level, you will need to use a pull-down resistor to avoid erratic reradings.

spitfire · 13th August 2007, 10:52 AM

Thanks again Mike, I did not know that, what value resistor should I use, is this for all unused inputs that need to be logic 0, do I need pull up resistors for logic high? yes I'm using the 4510's but when I first switch it on it displays a 2, but once it counts a full cycle and resets it works normally. doesnt really matter because I wont be displaying seconds but it would be good to know why this happens.

mike11298 · 13th August 2007, 11:09 AM

10k resistors are quite common to use. For example, if I have a count input pin, that is triggered when the pulse is HIGH (1), then there should be a 10k resistor to ground (note that this is unneccisary if you are using the output of another chip to get a signal. Thats because the other chip will allready have the logic at either 1 or 0, not (as its called) floating.) Generally speaking, if the pulse required to trigger something is a 1 (high) then the resistor should be to the ground , and vice-versa.

As to why your counter starts up at 2, Im not 100% sure. I do know, that it shouln't - it should start from 0 (BCD outputs all low). Perhaps stray charges are infiltrating your 'count in' pin, so try the resitors suggested. If that doesnt work, perhaps the power supple, but this seems unlikely (I am assuming you're using a battery? this would eliminate these issues).

Try the methods suggested, then see what happens.

spitfire · 10th September 2007, 06:41 AM

Hello again.
The 10K resistor worked a treat Mike.
I have completed my circuit and have built it all on veroboard but now I have one problem which I completely overlooked before.

I have attached my diagram and the problem lies in the areas circled in red.
My problem is that I was going to use the terminal count output from U3 to trigger U4 which works but I didnt realise that pin 7 on U3 was going to be LOW for a minute wich is how long the number 9 on the previous IC is being held for. I was thinking of putting an inverter on Q3 of U3 to trigger the clock enable input from U4 on the negative edge but I dont think that will work because the inverter will only invert the logic state hence producing the same problem as before...am I rite? basicly I need to get an active low signal to trigger CE on U4 once only for a second and not be held for the entire minute The same need to be resolved for U5...can someone give me some hints on how to overcome this? By the way please ignore the switches on the diagram as I have connected them differently.
I will post pictures when this has been fixed...I made a custom 4 number 7segment display from 58 blue LED's and Im eager to see what you all think of it.
Thanks

mike11298 · 10th September 2007, 10:20 AM

Have a look here: 4510 Counter its near the bottom of the page, and be sure to read the one on connecting them with a shortened count (just below).

Quote:

I didnt realise that pin 7 on U3 was going to be LOW for a minute wich is how long the number 9 on the previous IC is being held for.

This is solved by the NOT gate in the link i gave you.

Try this, and see what happens.

Quote:

basicly I need to get an active low signal to trigger CE on U4 once only for a second and not be held for the entire minute

Why? so long as there is a pulse, it should work. The clock output of the chip SHOULD be active low, and high everytime else. The input for the chip is the same, so they should work. Once again, see and try the link attached.

BTW, Have you built it yet, or is it still in proof-of-concept kind of thing?
If i'm missing something, please tell me more.

spitfire · 11th September 2007, 02:21 PM

Yeh, I had it built and tried the inverter method and it worked but only after re-cutting tracks and removing tiny solder splashes that took me a few hours to find...but it's finaly finished and its working!

let me know what you think.

I've been trying out different materials as a screen/filter for the leds because they have a terrible viewing angle. I'm going to try some frosted glass when I get a hold of some.

Hero999 · 11th September 2007, 06:51 PM

You could use frosted LEDs?

Failing that, try roughing them up with some fine emery cloth, do this on one spare LED first so you can be sure you're satisfied with the results.

spitfire · 12th September 2007, 01:37 PM

I had thought of that but I like the idea of a filter screen, the glazed glass I have fitted at the moment is acutally giving a nice glow and softens the intensity of the LEDs quite abit and looks good in both dark and well lit rooms.
I used some silicone to glue the glass to the edge of the veroboard flush infront of the LEDs.

blueroomelectronics · 12th September 2007, 02:30 PM

Spitfire that's a nice piece of work.

Yours to michael11298, what's the CDS cell for? a dimmer?

mike11298 · 14th September 2007, 09:40 AM

Thats a nice piece of work, spitfire. As hero999 suggests, I would file the LEDs somewhat flat (or close to) so they diffuse nicely.

Bill> the CDS cell is part of a dimmer system (I call it Dim-o-Matic

.. sorry..lol) that changes the display brightness in different light conditions. It is two-state only (that is bright and dim) and includes a capacitor to avoid nasty display flickering when the light levels near the threshold.

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12th August 2007, 08:32 AM	(permalink)
mike11298	yes, true, but if you like, you might want to use a 4520 dual bcd counter. it has two counters in one, but it is very fiddly and particular about its values. Basicly its a big hassle.. BUT the good news for you is that they are ridiculously cheaper (mine was 60cents compared to a single BCD at $1.40) and, i have already used them in a seconds configuration for my clock i showed you. If the chips are availiable to you, you might want to consider it, I will give you more info if that is so. __________________ -michael11298

12th August 2007, 01:39 PM	(permalink)
spitfire	Yeh I actually found 2 4520's that I got from work in my component stash but they did seem alot more complicated for someone at my level in digital to setup for a 24H clock. I emulated a seven segment display with 14 leds to test a 10 second counter and the number starts at 2...is this normal? or is it the 4000's series is slow to react and i need to place a cap somewhere to hold the clock pulse for a short period before it starts counting?

13th August 2007, 10:43 AM	(permalink)
mike11298	Are you using the 4510's? They should count (in binary) from zero to nine, then reset. If you need to reset earlier, you use an AND gate on the output pins to the input (in correct binary format for the number you want to reset at). Dont forget that even if you want an input to be zero or 0 logic level, you will need to use a pull-down resistor to avoid erratic reradings. __________________ -michael11298

13th August 2007, 10:52 AM	(permalink)
spitfire	Thanks again Mike, I did not know that, what value resistor should I use, is this for all unused inputs that need to be logic 0, do I need pull up resistors for logic high? yes I'm using the 4510's but when I first switch it on it displays a 2, but once it counts a full cycle and resets it works normally. doesnt really matter because I wont be displaying seconds but it would be good to know why this happens.

13th August 2007, 11:09 AM	(permalink)
mike11298	10k resistors are quite common to use. For example, if I have a count input pin, that is triggered when the pulse is HIGH (1), then there should be a 10k resistor to ground (note that this is unneccisary if you are using the output of another chip to get a signal. Thats because the other chip will allready have the logic at either 1 or 0, not (as its called) floating.) Generally speaking, if the pulse required to trigger something is a 1 (high) then the resistor should be to the ground , and vice-versa. As to why your counter starts up at 2, Im not 100% sure. I do know, that it shouln't - it should start from 0 (BCD outputs all low). Perhaps stray charges are infiltrating your 'count in' pin, so try the resitors suggested. If that doesnt work, perhaps the power supple, but this seems unlikely (I am assuming you're using a battery? this would eliminate these issues). Try the methods suggested, then see what happens. __________________ -michael11298

11th September 2007, 06:51 PM	(permalink)
Hero999	You could use frosted LEDs? Failing that, try roughing them up with some fine emery cloth, do this on one spare LED first so you can be sure you're satisfied with the results. __________________ I also post at the following sites: http://www.stop-microsoft.org http://www.heated-debates.com Screen name: Aloone_Jonez And http://www.silicontronics.com, same screen name as here.

12th September 2007, 01:37 PM	(permalink)
spitfire	I had thought of that but I like the idea of a filter screen, the glazed glass I have fitted at the moment is acutally giving a nice glow and softens the intensity of the LEDs quite abit and looks good in both dark and well lit rooms. I used some silicone to glue the glass to the edge of the veroboard flush infront of the LEDs.

12th September 2007, 02:30 PM	(permalink)
blueroomelectronics	Spitfire that's a nice piece of work. Yours to michael11298, what's the CDS cell for? a dimmer? __________________ Bill Smart Kits build Smart People http://www.blueroomelectronics.com Last edited by blueroomelectronics; 12th September 2007 at 02:34 PM.

14th September 2007, 09:40 AM	(permalink)
mike11298	Thats a nice piece of work, spitfire. As hero999 suggests, I would file the LEDs somewhat flat (or close to) so they diffuse nicely. Bill> the CDS cell is part of a dimmer system (I call it Dim-o-Matic .. sorry..lol) that changes the display brightness in different light conditions. It is two-state only (that is bright and dim) and includes a capacitor to avoid nasty display flickering when the light levels near the threshold. __________________ -michael11298