Hi all! First post as have been lurking for a bit.

Theres not much in the way of electronic forums out there, and google isn't proving much help either! This place looks like it could be really helpful though

I dont have a great deal of experience with electronics beyond highschool. I repair hifis for living, but vintage (pre-1970) only - so nothing like electronics in the modern sense!

I have a fairly simply project - a car speedo (Alfa Romeo in this case) that i wish to convert to a clock, with the warning lights working for on my desk at work.
A battery powered clock mechanism is a no-brainer of course - but i'd really like a clock mechanism that can be wired up with a couple of white led's and powered from mains with a 12v supply.

Any guidance on parts ideas would be useful - the clock mechanism (one thats small enough and can be powered from 12v anyway) is proving the pain, once found i could piggy back power onto a board for leds from there.


thanks!

 

A battery powered clock mechanism is a no-brainer of course - but i'd really like a clock mechanism that can be wired up with a couple of white led's and powered from mains with a 12v supply.

Most battery powered clock movements are lower voltage than 12 V so that they can be powered by fewer battery cells. However, it is simple to build a regulator circuit that will take your 12 V output and provide whatever voltage your chosen movement circuit needs.

What do you want the LED's to do?

I would be interested in seeing a photo of the Alfa-Romeo speedo you plan to use. Sounds like an interesting project.

 

To put the conversation into a course; You have a digital speedometer ripped from an Alfa Romeo and you want to convert it to a clock?

If it is so, it would help if you posted some pictures and listed the pinout of the display.

 

I assumed an analog speedo display and an analog clock display.

 

Hi guys,
thanks for replying - i'll post some pics tomorrow of the rev counter (sorry, i said speedo!).
Its a white face, and in the car would also display the indicator and warning lights.
I've removed the needle and needle mechanism already in order to do some prep work on it. The speedo face is effectively a piece of foil type material - with the parts where the lights are displayed simply being coloured (i.e. if you hold the dial up to a light you can see all the colours of the indicators etc). This is stuck onto a plastic face which has holes for the dioeds (which will be removed in order to fit a clock mechanism in there), which is in turn stuck to a pcb.

Sorry for this being totally vague! I know i could easily buy an off the shelf clock mech and shove it in there and job done - but it would be soooo much cooler if there was also a light in there so that all the warning lights (it is an alfa! lol) were visible too.

I'll post some pics in the morning. But to show you ther unit itself, heres one on ebay, you can see the warning lights etc present in the bottom right corner.

Thanks so much again for replying.

 

Is this the one?

http://www.ebay.com/itm/ALFA-ROMEO-...arts_Vehicles_CarParts_SM&hash=item2a16ae95cc

I think it's a cool project idea. What are you going to do about numbers for the time?

 

There are many quartz movements with hands available in square packages sized about 55mm on a side, and perhaps 15mm deep - the AA cell which is their usual power source fits in snugly. If this is small enough you could probably find one easily enough, either from a specialist supplier like this: http://www.clockparts.co.uk/clock-movements-repair-packs.htm

Or perhaps by dismantling a basic modern wall clock, many of which contain these items.

 

Hi guys!

Tracecom: Sorry, i didnt post the link! Yep, thats the one - pics below! Hopefully i can get this all to work, because i recently stuck an old alfa drivers seat to an office chair base (the seat was broken anyway, so it was heading for the skip!) and sold it on fleabay for over £120! So, once i have my own clock, there could be something in it to market to other enthusiasts.

Adjuster: Thanks for the link - they do hands for cd clocks, which would be perfect - and movements with 16mm spindles will certainly help things, as you'll see from the pics! A bit pricey though, but certainly the best i've seen so far! Thanks again!


So, on to the pics....(hopefully they appear correctly - sorry for the shoddy camera phone shots!)

The first is the rev counter with needle removed.
Pic 2 are its guts. The circuit board is possibly redundant now (?). As you can see from the rear of the counters face, theres a lot of moulded plastic in there which i guess i'll need to remove in order to fit a clock movement in there.
Pic 3 is how it will basically look when done, just imagine the clock hands on there for now. Thats the counters face, with its chrome bezel retained (will be glued on), and mounted on the plastic rear, giving it an overall depth of 6cm.
Pic 4 is why i would like somehow to work some illumination inside it too if possible!

Thanks for reading again guys, and thanks even more for your enthusiastic repsonses!

 

So, that is more than just the tach. It houses the turn signal indicators and other indicators as well. Immediately, all sorts of possibilities jump to mind. One would be to use a microcontroller to light individual LED's at different times. For example, have the LED's that illuminate the tach's red zone indicate an alarm.

But that's way more complicated than what you want. All you really need is a clock movement and a circuit to light a couple of LED's and regulate 12V down to whatever voltage the clock movement requires. That should be very doable, although it will require some soldering and some mechanical ability. For example, you will need some way to connect the regulator circuit to the clock movement's battery terminals. And of course you will need some way to mount the regulator/LED assembly inside the housing. Given the electrical circuit, can you do the rest?

 

Hi Tracecom,

Yup, all possibilites I can't execute probably lol! Seriously, the kind of electronics i deal with are so old capacitors are the size of D batteries lol!

The problem i see with having led's in there is that it'd be good to have them like the original pcb, which would mean retaining all the plastic gubbins inside the housing, which in turn would make it almost impossible to get a clock mech in there.
Plus, the clock would be running on 1.5v - and thats your lot!

With guidance i'm sure i could crack it - i have an iron and desk clamps/magnifiers etc that i use for my stereo stuff. In short i'm equiped, but clueless! lol!

Thanks again for the reply!

 

I think the following would work. All the resistors are 1/4 watt. I suppose you are in the UK, but presumably you have access to the LM317 regulator. Before you buy or build anything, let some of the more knowledgeable members here comment on the schematic.

 

I think the following would work. All the resistors are 1/4 watt. I suppose you are in the UK, but presumably you have access to the LM317 regulator. Before you buy or build anything, let some of the more knowledgeable members here comment on the schematic.

I've not seen something like that since highschool! lol! It may aswell be in Japanese! I vaguely understand what it all is, but need to do some research (sorry!).
What could i mount this all on to?

 

I've not seen something like that since highschool! lol! It may aswell be in Japanese! I vaguely understand what it all is, but need to do some research (sorry!).
What could i mount this all on to?

A small piece of vector board, vero board, perf board or similar. It should all fit on about 1 square inch or less. Of course, you may want the LED's off the board on wires so you can postition them where you want them.

 

ahhh, thats the board with the holes in right? Just push bits in, wire together, solder the reverse?

 

Typically these movements can be found for less than £5 ($7?) if you look around. Example (not particularly a recommendation): http://www.lainesworld.co.uk/L/CLOCKPARTS/CR131240.html That's not exactly pricey, in my view.

If you can fit in a clock movement like that, why not just run it on its battery. It would need changing maybe every year or two, but so what?

The LEDs could then be run from the supply using series resistors to define the current, if a steady light is all you need. If you have issues perhaps with eyesight or dexterity that stop you using very small parts, you might use resistors of a larger power rating than strictly necessary.

If you do not know how to calculate resistors for LEDs, somebody can advise you. Please do not try to get LEDs to a total voltage to equal the supply, without any resistor: this is unlikely to give a safe reliable result.

 

I think the following would work. All the resistors are 1/4 watt. I suppose you are in the UK, but presumably you have access to the LM317 regulator. Before you buy or build anything, let some of the more knowledgeable members here comment on the schematic.

@antpal: Perhaps you could comment on where you are: I do not think "high school" is so widely used here in UK as it is in the USA.
You would be able to buy LM317 if you live in this country.

If the supply is 12V, and the simplest solution is wanted, it may be better to put both LEDs in series, with a resistor of perhaps 330 ohms. (This would depend on the forward voltage and current ratings of the LEDs, I am guessing Vf≈1.5V, 12V input and running at about 15mA. )

Note that this circuit requires a DC input,

 

Hi Adjuster,
Thanks again for your input.
I'm in Norwich UK. It was called High School when i was there, so it's probably known as an academy, or eco home housing estate these days

I do find this a bit confusing, but at least im giving it a try and not settling for just bunging a clock mechanism in there.
Could the LED board be powered by something onboard, like a cr2 cell? Given the fact the clock will be battery powered too.

My original mention of 12v is that i have a load of redundant 12v dc power supplies knocking around which could be used.

 

It would be much easier if you decide to power the clock with a battery. You still can use the 12 V supply for three LEDs in series. (A small battery for the LEDs wouldn't last long.)

You won't need a PCB because you can just use the components' leads to connect them together. The schematic below should work for any common white LEDs you choose.

 

Note that some "12V" supplies designed for more than 12V maximum load might give substantially more voltage if only delivering 20mA or so. The answer is to measure the supply, initially off-load, and start off with a resistor calculated on that basis, revising it if necessary.

I would agree with the last poster that running the LEDs off a battery is not so good. If continuously on, depending how bright you would be lucky to get a week or two, whereas the clock should go for a year or more.

 

Note that some "12V" supplies designed for more than 12V maximum load might give substantially more voltage if only delivering 20mA or so. The answer is to measure the supply, initially off-load, and start off with a resistor calculated on that basis, revising it if necessary.

True. Some unregulated 12V supplies run as much as 16-17 V under light load. Measure the voltage and recalculate the resistor value.