Clock with LED

[jbelectric777]

Hey All.... Been a while since I been in here. I need some help on a project. I was wondering the best way to go about controlling 4 LCD 's for a real time clock. Is there a semi conductor timer chip micro controller or something like that. I did the NE555 timer and decade counter thing a few years ago just to get a better hands on as a hobby, but now I just need to place the numeric digits (red) on the front of a picture and mount the clock chip on the back, hopefully power it all by a very small batterie. Thanks in advance, I know you guys are pro's and Im just getting back into it as a hobby..... Jim

 

[vne147]

LCDs? Or LEDs? Is it like this:

https://image.made-in-china.com/2f0j00jBHQzfPtsDqS/7-Segment-LED-Display.jpg

 

[crutschow]

LEDs consume too much power to be powered by any reasonably sized battery. You would need an LCD display for that.

 

[jbelectric777]

vne, yes your both right, i dont wanna use led's i want something like the pic vne showed me, is that lcd or led and whats the difference, i know led is light emitting whats LC ? Jim

 

[danrogers]

an lcd is a liquid crystal display, the type found on traditional wrist watches etc.

 

[vne147]

LCD is liquid crystal display. The display you are interested in using is a 7-segment LED display. It's called 7-segment suprisingly because there are 7 segments that you turn on and off to make up the different numbers. Basically, it's a piece of plastic with 7 channels cut into it and inside each channel is an LED. Check this out for more information.

In answer to your other question they do make digital clock ICs some of which can directly drive the 7 segment displays. A quick google search brought up a few part numbers:

Sc8560
NTE2062
LM8560

I think most of these require either 50 or 60 Hz oscillator input to properly function.

 

[Space Varmint]

CD74HC4543 is usually what you use to drive LCDs. One for each digit.

 

[jbelectric777]

Everyone thank you sooooo much, I have another question: When using the NE555 for one second pulse, if time = RXC then do I have to adjust R or C for the trigger Vcc of 2/3 ????? Thanks again, Jim

If I can ever be of any help to anyone, I am a licensed electrical inspector and licensed electrical contractor. Maybe pay back the brain pickin I do ! Thanks again everyone. Im going to be starting a new thread on 555 timers. I wanna know everything I can about the 555 from 1-8, I know how to hook em up but I learned its better to know the "why" instead of just the "how" I understand logic circuits because I did a lot of industrial controls where I designed many motor control / PLC systems. IC's unlike line voltage equipment can be destroyed so easy and Im tired of runnin to RS for my components. I know Vcc + and ground -, trigger 2/3, output (max 200ma) but I dont yet understand: threshold, control voltage, reset (I think reset is just give it an input of Vcc+ and it resets itself. I am using it for a 1.0s clock (pulse)...... Thanks , Jim

 

[Space Varmint]

I don't like '555s so I'm not sure if they rig them for crystal clocks or not. You MUST use crystal!

Low power crystals are available at 32KHz. Check out Mouser for parts. I find there prices to be the best around.

 

[flat5]

Hello Varmint! How'z space? It's snowy here

SV is very correct. Don't use a 555 as your time base. Do use a crystal with gates.
You could use the 555 or 556 as an alarm.

 

[jbelectric777]

but if i use a UL listed power supply with a full wave rectifier power consumption shouldnt be a problem then right? I found a 120/9 VAC that i rigged 4 diodes to the output is max 200ma but i can buy a bigger one, what does the average LED 7 segment draw?

 

[vne147]

but if i use a UL listed power supply with a full wave rectifier power consumption shouldnt be a problem then right? I found a 120/9 VAC that i rigged 4 diodes to the output is max 200ma but i can buy a bigger one, what does the average LED 7 segment draw?

Does is 120/9 VAC? Are you refering to a transformer with 120 V primary and 9 V secondary windings or an AC adapter with 120 VAC input and 9 VDC output or something else? In answer to your other question, you can usually find the current segment draw of you LED display in its associated data sheet but a good ballpark number would be between 10 - 20 mA per segment.

Also, **broken link removed** is a fairly decent 555 tutorial. But as was stated already, I wouldn't use a 555 as your time base.

 

[Space Varmint]

You have decided you want LED instead of LCD? 200ma should be plenty. I found this for your LED driver:

**broken link removed**

 

[vne147]

You have decided you want LED instead of LCD? 200ma should be plenty. I found this for your LED driver:

**broken link removed**

That's good info but if he uses anyone of the 3 ICs I listed in post # 6 he won't need a dedicated driver as they are designed to directly drive the display segments.

 

[Space Varmint]

OK, I did not look at your IC's. I'm so confused I thought he wanted LCDs...LOL

 

[jbelectric777]

im sorry, i have everyone confused. im going with a 120V primary with 9V secondary transformer, and no its just a transformer ac to ac, i soldered in (4) diodes and made a rectifier, i have the 555 timer pulsing now and i wanna use the led segments cuz i have em in stock but for future reference you guys said ya didnt like 555's and for very low consumption i should go with LCD now after the pulse (1.0s) what do i need a counter??? (crystal)

 

[vne147]

im sorry, i have everyone confused. im going with a 120V primary with 9V secondary transformer, and no its just a transformer ac to ac, i soldered in (4) diodes and made a rectifier, i have the 555 timer pulsing now and i wanna use the led segments cuz i have em in stock but for future reference you guys said ya didnt like 555's and for very low consumption i should go with LCD now after the pulse (1.0s) what do i need a counter??? (crystal)

A crystal will be much more accurate so your clock won't drift as much over time. Also, the ICs I listed require a 50 or 60 Hz signal which means you need a pulse every 1/50 or 1/60 of a second. 1 pule per second is a 1 Hz signal. LCDs do have lower power consumption when compared to LEDs but since you're powering the project off of mains, it doesn't really matter all that much and in my opinion the LEDs will be easier for a beginner. -9V supply is fine for the IC. Can I assume you are using some large smoothing caps downstream of your bridge rectifier? Can you post a schematic of your power supply stage?

 

[vne147]

I found this. Might be helpful to you. This example doesn't use a 555 or a crystal, it uses and RC oscillator.

 

[Space Varmint]

I found this. Might be helpful to you. This example doesn't use a 555 or a crystal, it uses and RC oscillator.

No no no. Your clock will change speed if you walk in doors or expose to direct sunlight etc. Do not use RC. Use crystal!