Am I doing my math right? Each LED bulb is 5 watts @ 12v should be .42 amps. Is that correct?

The spec I've seen for #161 bulbs is about 2.7 watts. 2.7/12 = 225mA.

That means a digit with all bulbs illuminated draws almost 5 amps. 20 amps for 4 digits.

It's going to take a hefty ATX power supply to operate this clock.

 

Certainly there are many possible ways to implement the conversion to a decorative timepiece. My suggestion is based on the concept of not having to do a total change to every part of the system.The suggestions that I see involve removing completely every aspect of the previous arangement, including every interconnection wire. That will certainly make every step of the change a whole lot more effort.

 

My suggestion is based on the concept of not having to do a total change to every part of the system.

Those "parts of the system" aren't designed as a clock.

Consider the following:

● The time display on the scoreboard is designed to count down to zero. Therefore, the Ledex switches are wired to decrement the numbers on each pulse. Every time a digit on the clock changes, the Ledex switch would have to count 'all the way around'. This will result in a huge number of cycles.

● The scoreboard normally displays leading zeros, and may not have provision to 'display' a blank digit.

● Ledex switches are relatively noisy. Imagine cycling through nine steps every time a minute advances.

● Keeping the number of pulses sent in sync with the time could be troublesome.

Yes, Rube Goldberg could make it work, but probably not reliable over the long term.

 

Good point about the counting down. That would require a rewiring of the switching scheme to reverse the direction, which would be tedious but by no means needing a redesign. just careful attention and some good soldering ability. And certainly they could be replaced by a counter and a diode matrix, neither of which would require programming skills, nor consume a lot of power. A microcontroller is a rather poor choice to replace a counter in almost all applications. And the chance that the same micro will be available as a replacement in a very few years is not likely, while standard CMOS logic devices have been available for over 20 years and are still available from many producers. So if "sustainability" is a consideration, the micro is out of the discussion. A product designed for a long term application should be repairable.
Besides that, discrete logic is much simpler to analyze than most program flows.

 

Am I doing my math right? Each LED bulb is 5 watts @ 12v should be .42 amps. Is that correct?

Where will the clock be employed? If indoors, you don’t need (or want) 5W per bulb. It would be blindingly bright. The original was designed to be visible outdoors in sunlight.

 

Where will the clock be employed? If indoors, you don’t need (or want) 5W per bulb. It would be blindingly bright. The original was designed to be visible outdoors in sunlight.

This particular unit was made for a basketball court, so it is an indoor unit. It is made out of aluminum rather than a steel unit for outside. Furthermore, outdoor units were much better sealed, albeit, harder to get into. This unit is much more accessible, as far as pulling score digits out, etc.

 

The spec I've seen for #161 bulbs is about 2.7 watts. 2.7/12 = 225mA.

That means a digit with all bulbs illuminated draws almost 5 amps. 20 amps for 4 digits.

It's going to take a hefty ATX power supply to operate this clock.

I was going to make my own power supply out of an old pinball transformer. VERY heavy duty iron transformer, meant for continuous use with 6.3v and 12v output. I was going to wire that into a bridge rectifier and call it good. Any thoughts to the contrary?

 

This particular unit was made for a basketball court, so it is an indoor unit. It is made out of aluminum rather than a steel unit for outside. Furthermore, outdoor units were much better sealed, albeit, harder to get into. This unit is much more accessible, as far as pulling score digits out, etc.

Okay, I still think it will be too bright with 5W LEDs. A basketball court is likely lighted well above what a typical room is. You won’t know until you try it.

 

Are these LEDs or incandescent lamps?
If all the lamps you need are there, you can operate the lamps at a lower voltage instead of 12V.

 

I was going to make my own power supply out of an old pinball transformer. VERY heavy duty iron transformer, meant for continuous use with 6.3v and 12v output. I was going to wire that into a bridge rectifier and call it good. Any thoughts to the contrary?

A few, that's for sure....

First, the bulbs don't care whether it's 12VAC or 12VDC, but DC will be a lot simpler to control. But each digit potentially draws 5 amps, if all 8 digits have every bulb on, that's 40 amps. That's going to be difficult to supply.

In the scheme I've suggested, adding dimming is a not-too-difficult option. I agree with @BobTPH that the bulbs may be too bright.

One way to deal with the large power demand and the probably way-to-bright issue, since printed circuit boards need to be made anyway, would be to design new digit boards using LEDs mounted directly to the board.

Electronically, this is straight forward. Mechanically, it might be a challenge to get the LEDs positioned the correct distance from the lenses.

Questions to determine practicality of this approach:

1. Are all 8 complete digits the same size?

2. Do you want/need the leading "1" on the score box numbers?

3. What is the physical size of the individual digit boards? What is the physical size of the pair of digit boards (i.e., is a single larger board for a pair of digits practical?)

4. How do the existing digit boards mount? I don't see any hardware to fix them in place.

Can you take pictures of the front of a digit board, as the assembly looks when pulled out from the scoreboard? Don't take anything apart, I just want to see the front of the digit assembly if possible. And a view of one digit one the scoreboard, looking back to front? If possible.

 

Are these LEDs or incandescent lamps?
If all the lamps you need are there, you can operate the lamps at a lower voltage instead of 12V.

I was actually thinking that very thing as I wrote the above. I wonder if there's a spec sheet showing current draw and lumens vs voltage.

 

You can use CD4017 decade counters to do the counting but the diode matrix is a mess. You would need about 50 diodes for each digit. The MCU solution still seems the better option to me.

 

Looks like 0.1" pitch or at least close enough.

I count 8 spaces in 1.6", for a 0.2" pitch.

ak

 

Besides that, discrete logic is much simpler to analyze than most program flows.

Agree. And, incandescent bulbs *hate* multiplexing, There are many ways to de-mux a few uC output pins to a bunch of static displays, but that adds software layers while you still need discrete chips to latch, decode, and drive. Now that later CMOS parts have some of that built into a counter, I don't see a useful savings.

OTOH, having nothing but a single coax between the brains and the display is a nice bit of design. It looks like they basically grew a custom UART from scratch. Here is where a uC would be very handy.

I don't know if this has come up already, but one approach is to start with turning the displays into LED-equivalents with one chip to convert BCD to 7-segment drive, plus a bunch of lamp drivers. From there, any clock circuit with BCD outputs can drive the displays. A disadvantage of using a decoder chip is that you lose the original digit shapes, which were not simple bar segments.

Has anyone brought up putting a clock chip in the display, and remoting only the set controls?

CMOS came out in 1968, so 55 years and ***counting***.

ak

 

Are these LEDs or incandescent lamps?
If all the lamps you need are there, you can operate the lamps at a lower voltage instead of 12V.

All the lamps in the machine are incandescent right now. I would convert them to LED if there was a power savings. Since I am not tied to using anything from the original machine except the displays, I am sure I can find a bulb that is better for both indoors and power savings.

 

I count 8 spaces in 1.6", for a 0.2" pitch.

ak

I stand corrected. Thanks for spotting that.

 

All the lamps in the machine are incandescent right now. I would convert them to LED if there was a power savings. Since I am not tied to using anything from the original machine except the displays, I am sure I can find a bulb that is better for both indoors and power savings.

If you have enough lamps I would use it as is but with reduced supply voltage.

 

If you have enough lamps I would use it as is but with reduced supply voltage.

Makes sense

 

LED lamps kill the ultra-retro look, but an advantage is that they draw way less current. This lets you use ULN-series driver chips, where you get 7 or 8 device drivers in a standard DIP package. Each driver can sink 1/2 A, which is fine for one bulb at 225 mA per, but there is a max current limit for the part, so all 7 or 8 cannot be on at the same time. Other driver chips have only 4 per package, but can handle the total current. Operationally, there is no difference between these chips and their equivalent discrete circuits; it's just a lot less wiring and soldering, and fewer joints to go bad over time.

Still, the old bulbs would be tres cool.

ak

 

LED lamps kill the ultra-retro look, but an advantage is that they draw way less current. This lets you use ULN-series driver chips, where you get 7 or 8 device drivers in a standard DIP package. Each driver can sink 1/2 A, but there is a max current limit for the part, so all 7 or 8 cannot be on at the same time at 225 mA per channel.

Still, the old bulbs would be tres cool.

ak

So, one thing with this unit is that the bulbs are behind a lens that is back lit. That's how green and red 'lights' are made with the scoreboard. The bulbs are not visible from the face of it at all. If the voltage was dropped to say 6.3v like in a pinball, I can buy a litany of LED bulbs that range from dim to extra bright. I also don't really want to change burned out bulbs every month. This will be mounted about 12 feet up in my barn.