DIY modification: let the alarm clock use rechargeable batteries

After my mobile phone alarm and bracelet reminders often failed, which caused me to oversleep and be late, I returned to the most primitive alarm reminder.

Of course, the mainstream alarm clocks are electronic alarm clocks now, because the traditional mechanical alarm clocks make a ticking sound when they run seconds, which is very sentimental, but it is particularly disturbing to rest.

However, I don’t know if you have noticed a problem. The batteries used in these alarm clocks are all 1.5V No. 5 batteries, which is nothing, but the rechargeable batteries are all 1.2V, whether No. 5 or No. 7.
This is very troublesome. It

’s not expensive to buy batteries frequently, but it’s even more troublesome if you suddenly find that the battery is out of power in the middle of the night.
Therefore, I tend to use rechargeable batteries.

At first I didn’t pay attention, but later I found that the newly charged battery installed at night did not ring the next day. Judging from the time, it often stopped not long after I fell asleep.

After suspecting that the alarm clock was broken and replacing it, I finally found out that it was because the voltage of the rechargeable battery was too low. The reason why it ran for a while at the beginning was that when the rechargeable battery was fully charged, the voltage was 1.4V, but it would drop back quickly, so it could run for a while.

For this reason, I searched Baidu for a long time, but I couldn't find an alarm clock movement that uses 1.2V batteries.
I also didn't find a 1.5V rechargeable battery.

So the way in front of me is very simple, that is, to do voltage conversion.

At the beginning, because I remembered my alarm clock wrongly, I thought it was 2 No. 5 batteries, so it was 3V, and 3 No. 1.2 happened to be 3.6, and the extra 0.6V could be reduced by a simple diode.

So, this is actually a very simple DIY, simple in principle.
But this time, because it is to be embedded in an existing ready-made item, I hope to seamlessly transform it in workmanship so that it will not affect long-term use.
The following is the process I made and the pictures I took. In fact, it is really simple. The point is that I hope to find a more seamless method that does not affect the appearance of the alarm clock

-especially, reject a bunch of wires, which is not only ugly, but also easy to cause it to break later.

And, it cannot be damaged. When I have to use the original 1.5V ordinary dry battery.

That is, when I add a new interface, I must keep the original interface and cannot damage it.

1. Because we need to avoid the wires, we must disassemble the casing and find a way to enter the wires from the battery box without making another hole.



2. Add a diode, and for safety reasons and to protect the device, add a heat shrink tube.



3. Assemble it back and add the battery box

4. Fix with double-sided tape

6. Basically completed

But in the end I found that it was actually one battery, which was 1.5V. I was a little hesitant at the time.
Because two batteries are 2.4V.
The common silicon tube voltage drop is 0.6 to 0.8, and the default is 0.7.
So the voltage is 1.7V, which is a bit high.

But in the end, since I couldn't find a better solution and voltage regulator for a while, I just did it this way.
But there is a problem, that is, it still doesn't last long, which I am very surprised.

Later, I considered using a low-voltage difference 1117-Adj tube to try.

(But because I don't have it on hand, it's more troublesome to buy it. So this part will be presented later)

A follow-up question is
For the sake of aesthetics, which is also my first reaction, I fixed the battery box behind the case.

But in fact, that position is not very good

First, that position happens to be the sound hole of the alarm clock, and it is blocked after it is attached.
Second, although it can be put in, it is very troublesome to operate the buttons for several alarm switches and time adjustment.

So, I will consider changing the position later.

One more thing to add is that although this kind of small production is basically simple in terms of circuit technology, there are still many considerations in the production.

For example, the battery box I bought happened to have a switch, so it was not a whole piece that could be fixed with double-sided tape.

So, I was very entangled at the time, and then I thought of a very clever way.

Anyway, I have to fix this switch, and I don’t want to disassemble it.
I just turned it to the open position, and then used cardboard to pad it up piece by piece and layer by layer.

This can not only prevent the switch from being moved, but also make the entire battery box sticky.




2. Final product. The battery box must be easy to open and close and change batteries.

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