I needed a small-sized lamp on a clothespin to illuminate books and for additional lighting for all sorts of small jobs.
The main requirements were:
- food — strictly from the battery (so as not to go broke on batteries);
- to shine — brightly;
- the location of the light source is on a gooseneck corrugated tube (so that you can change the direction of the light).
After studying the proposals on the notorious Chinese site, the choice fell on an advanced lamp on a clothespin with 7 LEDs, 4 of which are “cold” and 3 are “warm”. Moreover, LEDs can work both all together, and individually “cold” or “warm”.
Image from seller’s page on Aliexpress
The price on the date of the review is about $ 8.4, including delivery; in the future, the price can change in any direction (link at the end of the review).
Packing and construction of a book clip lamp
The lamp arrived packaged in a solid corrugated box, which was almost undamaged in transit.
The packaging indicates the main purpose of the lamp from the manufacturer’s point of view: to illuminate musical notes (we will also check this!).
On one side of the box this is reported in English, and on the other in German:
Here and below, all images are clickable.
At first glance, the pictures on the packaging for the «English» and «German» versions of the description are the same. But if you look closely, you can see that the «English» version is two-headed, and the «German» one is single-headed! The review considers a single-headed version. A two-headed one can also be found on sale, but it does not work on batteries, but on batteries; and therefore of little interest.
In order for the lamp to fit inside the box, its gooseneck was folded into a couple of turns.
This is what the lamp looks like unfolded:
If the “goose neck” is fully extended, then its length is 17 cm.
«Gooseneck» can be bent in any direction (provided that these are smooth bends); and you can also rotate around its axis the lamp located at the end of the «neck».
You can definitely rotate the lamp around its axis at an angle of up to 180 degrees; more — did not try (because there is no need).
Side view of the lamp:
The bottom of the clothespin contains a lithium-ion battery and its charge controller.
Behind this «stand» are a pair of LEDs and a micro-USB connector for connecting a charger:
The LEDs work as standard: red glows during charging, green — at the end of it.
The battery is located in the thickened (lower) part of the clothespin. The upper part of the clothespin is thin, it serves only to hold the clothespin on the object to which the lamp is attached.
Thanks to the flat bottom of the clothespin, you can simply put it on the table; but the neck in this case should not go far beyond the projection of the center of gravity of the structure, otherwise it will fall.
The upper part of the clothespin ends with a small platform, which is attached to the main part of the clip with a loop, and therefore can be rotated up and down a small angle.
A rubber plate with a “protector” pattern is glued to the underside of this platform, preventing the clothespin from slipping off the surface on which it is fixed:
Thanks to the strong spring and embossed rubber plate, the lamp holds well on surfaces with parallel sides.
At the end of the «gooseneck» is a lamp with a single control — a button on the top side.
As the autopsy will show further, the matte diffuser has an uneven thickness.
By successively pressing the button, the lamp operation modes change: cold light –> warm light –> neutral (maximum) light –> off.
Dismantling the lamp on a clothespin (almost complete)
The lower part (stand) is fastened with only four screws:
After unscrewing them, you can separate the halves of the stand:
On the lower (pictured) half is the battery, firmly held by the «paws».
The capacity rating on the battery is not indicated (or it is located under a blue protective film and therefore invisible). We’ll have to figure it out in the laboratory.
On the top half of the stand is a board with a battery charge controller. Control discharge (protection against overdischarge) is not included in its functions; the wires towards the lamp go straight from the battery.
Let’s look at the controller board from the side of the elements:
The controller itself is a small 6-foot chip. Almost no binding is required.
Also on the board is a micro-USB connector for charging the battery and a pair of LEDs to indicate the charging process.
Now we proceed to disassemble the lamp lamp.
To remove its halves with a diffuser, it is enough to unscrew just one screw. And here we get:
The diffuser on the upper half of the lamp (pictured) is not glued to its frame to death, but simply inserted.
This is a very positive fact, since it will allow you to use the lamp in two versions: both with a diffuser and without it. And for what situations the first or second option is more useful, we’ll figure it out further.
At the “bottom” of the lamp there is a board with 7 LEDs in two colors, and around it there is a reflector so that all the light is directed outward.
Let’s turn the reflector over to look at the LED control board:
On the board are located: a button, with the help of which the modes are controlled; a pair of key transistors and a 6-leg controller with poorly legible markings.
Next to each of the transistors is a 2 ohm resistor to limit the current given to the LEDs.
Important note: LEDs are powered by direct current, there is no PWM!
And finally, let’s reassemble the lamp, but without a light diffuser:
This is the slight modification of the lamp mentioned in the title. Its effectiveness will be tested further.
Let’s see how the LEDs shine in complete darkness (with a diffuser). From the photographs it may seem that they do not shine brightly; but this effect in the photo was created forcibly (due to shortening the shutter speed) so that the internal structure of the lamp could be seen.
Only cold LEDs are on:
Now — only warm LEDs:
And finally, all together:
From the photos, it seems that the LEDs on the right shine brighter than the rest. This effect occurs due to the fact that the right side of the diffuser is thinner and transmits light better. This is not a defect in the manufacture of the diffuser, but its design feature (the diffuser continues the “drop” shape of the lamp as a whole).
Without a diffuser, there is no such effect, all LEDs of the same color shine the same way.
The heating of the lamp luminaire turned out to be significant.
To check the heating, a contact sensor in the form of a cylinder 20 mm long and 4 mm in diameter was used, placed close to the LEDs with the reflector removed.
The measurements were taken with a fully charged battery, and they showed the following results:
- only «warm» LEDs are on — 57 degrees;
- only «cold» LEDs are on — 61 degrees;
- all LEDs on — 76 degrees.
With a diffuser inserted, the temperature of the LEDs may be even higher due to poor ventilation.
In other words, the consumption of the lamp is significant, which leads to such heating. But this heating is internal, touching the outer surface of the lamp is not dangerous (only a feeling of intense heat, but nothing more).
Now is the time to look at this clothespin lamp in action.
Technical testing of a lamp on the example of an e-book
We will check the operation of the lamp on an electronic and on a real (paper) book, let’s start with an electronic one.
Now most e-books are released with backlighting, but there are exceptions.
For example, e-readers with an unbreakable screen on a plastic base are never backlit (apparently, the limitations of the technology work). Of course, such screens can be corrupted in other ways; but we will not consider these methods, since stupidity, as you know, has no limits (reason has).
In the experiments, this kind of electronic book ONYX BOOX Gulliver with a 10.3-inch screen was used.
First, some personal impressions.
From the photographs, it seems that the “cold” and “warm” backlights have too “thick” color tint, which will be unpleasant for the user (especially “warm”).
In fact, our vision, like a camera, has an automatic white balance; and a minute after viewing the book with such illumination, its hue does not seem to be somehow oversaturated.
It is advisable to place the lamp not above the surface of the book, but slightly outside it; otherwise, the reflection of the lamp in the screen will interfere with reading (even the matte surface of e-book screens, which «smear» the reflections, does not help — it’s checked).
The next note: if the frame of the e-book is narrow, then in order for the lamp to hold well on the book, it has to be placed with the lamp’s clothespins partially on the screen (seen in the photo). To prevent the clothespin from blocking the text, you can set the top reading field in the e-book settings a little wider than the rest.
And one more note: the brightness of light on the far side of the book from the lamp turns out to be noticeably lower than on the near one (which is quite consistent with the laws of geometric optics).
In this regard, ideally, it is better to use the lamp not in complete darkness, but at least with a little external lighting, the “additive” of which on the far side of the book will be more noticeable and partially smooth out the uneven illumination.
By the way, labor protection generally prohibits the use of local lighting alone. According to the guidelines, general lighting of the room must be mandatory!
Otherwise, there will be excessive contrast between the work surface (which is illuminated by the lamp) and the general background, and this is unhealthy. It is for this reason that doctors from ancient times did not recommend watching TV with the lights completely turned off.
The next experiment is lighting with a lamp with diffuser removed (“cold” light, but this is not important here):
First, it should be noted that the radiation pattern has become narrower; and secondly, due to this, the brightness of light within its main “beam” has increased.
Despite the sharpening of the radiation pattern, the screen of the e-book remained fully illuminated, and you can use the lamp with this modification.
Finally, the last experiment with the e-book.
As mentioned at the beginning of the review, the manufacturer positions the lamp as designed to illuminate musical notes. This is exactly what we will try to do (neutral light, diffuser inserted):
I am not a musician, and I am not sure about the convenience and usefulness of such a design, but from a purely technical point of view, everything works.
Next — testing on a real (i.e. paper) book.
Technical tests of the lamp on the example of this (paper) book
The book «Tales and Stories» by Vitaly Bianchi was used as a test book. For those who haven’t read it, I highly recommend it. The book is devoted to the interaction of man and the animal world; but there are very pitiful moments, in childhood even tears welled up!
Okay, enough lyrics. The book was chosen not for this, but for the «most average» page size (specifically 125×197 mm) and for the fact that the book has a hard cover (this turned out to be important).
In order to make it convenient to leaf through a paper book, the lamp must be put on a hard cover; leaving the lamp pages above the clothespin.
An attempt to use the lamp on a paperback book by clamping a group of pages with a clothespin was unsuccessful: due to the bending of the pages, the lighting was extremely uneven, and in general it was inconvenient to use the lamp.
So, we start again with the «cold» light:
The pages of the book are slightly yellowed from time to time, and therefore the color shade of the pages turned out to be slightly shifted to the “warm” side relative to the e-book.
The next photo is lighting with a modified lamp (with the diffuser removed):
As you can see, for a «real» book, the radiation pattern of the modified lamp turned out to be too narrow: it is not able to capture the entire spread of the book at once. This will not work!!!
To the heap, in the same chapter we will briefly consider the use of a lamp to illuminate the workspace for all sorts of small jobs:
The lamp is suitable for work with small objects; for example, soldering small circuit boards.
In this case, the lamp light can be used in addition to the main lighting. There may be some other applications when it is necessary to enhance the lighting in a small space.
For some large work, this lamp, of course, is not suitable.
The autonomy of the lamp on a clothespin
A feature of the lamp is the absence of a battery protection circuit from overdischarge.
Because of this, there is no certain moment in the operation of the lamp when the lamp would turn off completely due to a decrease in the battery charge below a critical value (for different versions of lithium-ion batteries, it is 3 — 3.2 V).
And, frankly, this is bad.
As a result, the user can assess the degree of charge of the battery only by indirect signs — a decrease in the brightness of the light or a decrease in the heating of the lamp. Methods, to put it mildly, are not very accurate. Sometimes the battery can get into a state of overdischarge, which will shorten its life.
In this regard, the duration of battery life was determined conditionally, «by eye», by reducing the brightness. At the same time, the final voltage of the battery turned out to be in the range of 2.9 — 3.2 V (it was difficult to keep track of it more precisely).
The results came out like this:
- only «warm» LEDs are on — 5 hours 10 minutes;
- only «cold» LEDs are on — 4 hours 20 minutes;
- all LEDs on — 2 hours 20 minutes
Consumption was measured at a battery voltage of 3.7 V, which corresponds to a charge of 50%:
- only «warm» LEDs are on — 190 mA;
- only «cold» LEDs are on — 220 mA;
- all LEDs on — 380 mA.
To reduce consumption and reduce lamp heating, you can solder a small resistor in series with the power wire coming from the battery towards the lamp; for example, 0.5 — 1 ohm. But the power should not be microscopic, not less than 0.5 watts.
I soldered a 0.5 ohm resistor. At least, this reassured me in the sense that the LEDs do not unsolder themselves in the maximum brightness mode with the most charged battery.
Since there is no marking on the battery indicating its capacity, I had to install it experimentally.
Charging the battery via a USB tester showed that 1094 mAh was poured into the battery (can be rounded up to 1000 mAh):
The charging process itself proceeded unevenly: the charge current started from 0.33 A, then increased to 0.48 A, and decreased to 0.1 A towards the end of the charge.
But the final charge time, despite these fluctuations, was 2 hours and 45 minutes, which is quite normal for lithium-ion batteries without a “quick charge” system.
Results, conclusions, recommendations
Here, it would seem, is such a simple product (a lamp on a clothespin), but how deeply you can “dig” into its properties!
I didn’t even expect this.
In the process of these “diggings”, many positive properties, as well as not so, were discovered.
- battery powered;
- high brightness lighting;
- the ability to adjust the color temperature of the lighting;
- no lighting flicker (no PWM);
- good uniformity of the light flux (no «spots» of bright and weak light);
- the possibility of modifying the lamp by removing the diffuser (sharpening the radiation pattern with increasing brightness);
- the ability to use the lamp while charging.
- no brightness stabilization (falls as the battery is discharged);
- there is no brightness adjustment (more precisely, it changes along with the selected color temperature; the smallest is in warm light, the largest is in neutral, when all LEDs are on);
- There is no battery overdischarge protection.
- in order to avoid overdischarging the battery, try to charge the lamp more often, it will not get worse from this;
- Use the lamp in at least some general light. This is a general safety recommendation that it is not recommended to work only with local lighting.
Despite the presence of these shortcomings, but the overall price-quality ratio is quite good.
The lamp exists in slightly different designs, you can check the current price of the lamp or buy it at this link on Aliexpress. The price on the date of the review is about $ 8.4, including delivery; in the future, the price may change in any direction.
Thank you all for your attention!