Introduction: Quartz Clock Power Supply Hack (AA Battery to AC Power)

I had a quartz wall clock in my workshop that ran a AA battery power.  The battery died so I decided that rather than buy a battery, it would be more fun to convert the clock from battery power to AC power.

Step 1: Tools

For this project, the only tools that you'll need are a soldering iron and (optionally) a hot glue gun.

Step 2: Parts

You will need:

(1) 5V power supply .. I used an old phone-charger .. these can be readily found at any thrift store
(2) 22uF caps rated for 10V or better
(3) silicon diodes .. I used 1N4936 because it's what I had lying around .. but most any silicon diode will do .. the forward voltage drop will vary slightly for different diode types, but this circuit is fairly tolerant of small voltage differences.
(1) 1K resistor .. the power rating doesn't matter much, the resistor will only need to handle milliwatts of power

Step 3: Schematic

Here is the schematic ..

Step 4: Point-to-Point Wire the Circuit

Just connect up the circuit as per the schematic.  Keep the leads relatively short so the entire circuit will fit in the space that was previously occupied by the AA battery.  Once wired, you should check the output voltage with a multimeter.  It should be somewhere between 1.5V and 1.6V

Step 5: Hot-Glue the Circuit in Place

This is somewhat optional, but it's nice to encapsulate the circuit ..

Step 6: We're Done ..

Sit back and admire your work :)


robrhy made it!(author)2017-02-08

Can't follow schematics.Anyone have a drawing of how to wire this up please.

HuaY1 made it!(author)2016-12-09

can i know which is + and - cable power?

scd made it!(author)2016-12-09

You will need a voltmeter.

plojm made it!(author)2016-11-29

I had 1 47uf 25v cap and tried to use that instead of 2 22uf ones, it seems to work for a little then not work. What is the formulat i get almost 1.6vs out exactly but ma s of power i dont know. u can hear the clock tick sometime then slow down for some reason

MaxwellF4 made it!(author)2015-12-23

I've come across this tutorial thinking of ideas for a lamp I want to build.

If someone is still reading these comments, I had a few questions regarding the wiring.

First, my idea is to build a desktop pipe lamp (like a steampunk style) with one or two bulbs, but also add a small clock to the mix. I like the design of some of the lamps with old gauges, and figured I could replicate the look, but have a clock instead that's fully functional compared to a gauge that's decorative. I would like the whole fixture to run off AC power though, and every small clock (4" or less in diameter) I would find would run off batteries of some sort (many which are AA that I have been looking at.)

For this setup, could I incorporate the circuit for this setup into wiring for a lamp? I'm a little confused with the diagram on what goes where also. According to the diagram, there is a ground wire that comes out, a wire that has 5v, and a wire that has 1.5v. Which of these wires is attached to where the battery would be, and is there only one wire that goes back to the wall plugin then?

To me, it looks as if the ground wire is the only wire that goes into the wall outlet (but I'd think the 5V one comes from the outlet, as you can see I'm confused here.) If the ground wire is the only wire heading to the wall outlet, could that be incorporated into the ground wiring for the bulb/bulbs for the lamp?

Worst case scenario for me, I'd just incorporate two different plugs for my fixture. That way I could setup the lamp portion to be on a remote outlet and the clock to be continuously on. Having one plug for the entire setup would be nice though.

Anyways thanks for any help and nice tutorial too. At the very least the tutorial will give me some more ideas on what I want to do.

scd made it!(author)2015-12-28

Hi Maxwell,

There are 2 wires (+5V and GND) that you need to connect from the 5V phone charger to the schematic in Step 3.


---------- original message ----------
From: MaxwellF4
Date: Dec 27, 2015. 9:19 PM

Oh okay. It appears that the 5V phone charger only has one wire coming from it. If that is so, do I just take that one wire (after cutting off the phone charger portion and unsheathing it) and splice it anywhere along the diagram in step 3, such as after the diodes?If so then that sounds very simple. Thank you for taking the time to respond also!

scd made it!(author)2015-12-24

Hi Maxwell,

Nothing in the schematic of Step 3 connects directly to AC power. If you look in Step 2, you will see a 5V DC power supply (a re-purposed phone charger). The 5V DC output of this power supply connects to the circuit of the schematic of Step 3. If this is still confusing to you, then please let me know.


MaxwellF4 made it!(author)2015-12-27

Oh okay. It appears that the 5V phone charger only has one wire coming from it. If that is so, do I just take that one wire (after cutting off the phone charger portion and unsheathing it) and splice it anywhere along the diagram in step 3, such as after the diodes?

If so then that sounds very simple. Thank you for taking the time to respond also!

nathanziarek1 made it!(author)2015-11-29

(Hopefully someone is still reading these comments!)

I have a project where I'm building something like clock wall they show in movies involving the President (you know, the ones that show DC time, London, Shanghai, etc).

I have four clocks that I bought from a thrift store, so there's no information on them. Each take a single AA battery and are just the basic second / minute / hour hand configuration like the one shown in this instructable.

I have a 6v adapter providing 500 mA. My questions:

1. I have no idea what the draw is of these clocks, but I have to assume its low. Will 500mA be enough to run all four of these?

2. If this will even work, I assume I'll be wiring these in series, not in parallel, correct?

Appreciate your time!

scd made it!(author)2015-11-29

The current draw for each clock is very low and it is not constant; most of the current draw happens once per second when the second hand ticks and (if I recall correctly) it was less than 1 mA for the clock that I used.

If you are going to build the power supply hack (as described in this instructable) for each clock, then you would run the 6V to each clock (in parallel).

It may be simpler to build a single 1.5V power supply using a MCP1702T voltage regulator and then run the 1.5V to each clock (in parallel). As an experiment you could wire all 4 clocks (in parallel) and try running them from a single AA battery. If this works, then great. If it acts funky, then you may need to add a cap to each clock to help supply the instantaneous current draw when the second hand ticks. Some experimenting will be needed on you part, but that's all part of the fun :)

Here is a digikey link for the MCP1702T 1.5V regulator:

And here is a link to the MCP1702T data sheet:

nathanziarek1 made it!(author)2015-12-01

I'm sure you're sick of being volt-guy tech support, but I'm wondering if this device would work: It's more expensive than the 50¢ regulator you mentioned, but for the project, I kind of like that it has a LCD display.


scd made it!(author)2015-12-01

Looks cool :) I think that would work fine for your project.

nathanziarek1 made it!(author)2015-11-29

I really appreciate your taking the time to respond.

I'm really new to this, so I was making the mistake that, because 4 clocks needed 1.5v each, I could use my 6v supply and just "spread" it among them.

Seems like this project might be a bit beyond me, but your instructable and response really helped! Thanks much!

kurt.saldutti made it!(author)2015-04-11

Thanks so much. We have quite large kitchen quartz
movement clock that actually has a pendulum that is moved by the clock motor.
Needless to say it eats AA batteries and the clock takes a 6" step ladder
to change the battery. It’s getting real old. I’m going to make up your circuit
ASAP and plug the supply in to a receptacle I already have up in the attic just
need to extend the 5V supply cable and add a Molex quick connect at the back of
the clock. Thanks again.

scd made it!(author)2015-04-11

Hi Kurt,

The circuit in this instructable can only supply a small current. If your clock also drives a pendulum it might need a better voltage regulator perhaps something like this:

Let me know how it goes and if I can be of any help.


scd made it!(author)2011-08-01

>> "I bet it easily chews more on your electricity bill than one cheap battery"

Here in the pacific Northwest, I pay about $.08 per kWh for residential electricity. This clock power supply circuit uses about 17.5 mW. So here is a rough calculation of the cost to run this clock for one year ..

$.08/kWh x (.0175Wh x 24 x 365) / 1000 = $.012 per year


tilt_u made it!(author)2011-08-15

It is correct that the circuit doesn't use much. But there's also the loss in the PSU which at very small currents are extremely visible if calculated in %. (I can see you use a switchmode which has the potential to use lot less standby power than an old iron core. An iron core typically has a standby use of a few watts).
Since that's a joker which has to be measured we can't fint out if it's actually cheaper.
Also I don't know what a discount alkaline battery costs in your country but here it's available for what is less than USD ½.

But really it's not the cost that concerns me most. It's the power out issue as a normal quartz clock will resume from where ever it was and cause you to not immediately notice the time shown is incorrect.
Also a standard quartz clock is not very precise so to stay within acceptable offset from real time you have to adjust it at approx. once a year anyway (if you're lucky it's too fast so just cut the power for a few moments). An ordinary consumer quartz movement today is specified to be within 0.5 - 2 seconds pr. day. Typically somewhere between 0.5 and 1 second can be expected of the ordinary consumer movement except for very few lucky samples (majority are specified within 1 sec but can also be specified for 0.5 for the best or 2 sec for discount movements). Even 0.5 sec/day which to many people doesn't seem as much accumulates to 3 minutes/year.

The power out issue you can deal with however. It can really be almost as simple as a triac and a push button. So if power fails the clock won't restart automatically upon return of power and you'll notice immediately it's wrong. Push the button to start the clock (and of course set it again).

Or why not just make something with a few super capacitors and a solar cell to skip mains power altogether if you really want it to be battery less?

tilt_u made it!(author)2011-07-20

Can't decide whether this is a good idea other than just for the fun of it.
I bet it easily chews more on your electricity bill than one cheap battery costs every year.

Also since it's not radio controlled you can easily be confused whether it shows the correct time if there has been a power out while you've not noticed it since the clock will run again afterwards. With a battery it'll stop when it's out of power so you will instantly notice if it's wrong.
You can instead use an RC movement with all those benefits they have but then you need to use a good power supply without high frequency noise (the easiest and most durable is an old fashioned one with iron core transformer).
Also you can add a backup with a super cap in parallel with the movement but I bet you need more than just a small one to get any significant run time.

If you want long run time before having to chance the battery I'll recommend putting in several single AA battery holders and wire them in parallel to feed the clock. And (very importantly!) install those energizer AA "L92 1,5 volt" lithium batteries in them. Important because ordinary batteries will leak before they're even half empty if used in such long time application. Also important to only parallel connect batteries of equal charge state. So when finally replacing them take them all out before putting the new ones in. Voilá. With a small handful of them you'll have a clock that easily runs for 8-10 years and even 15 or more is possible.

tilt_u made it!(author)2011-07-20

Sorry. The 1,5 volt AA size Energizer lithiums are called L91. L92 are the AAA's and since they're pretty much same price it doesn't make sense to use them except if space is tight.

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