To organise the workshop, I have developed a storage box for CR2032 and similar batteries of this type. There are already a few, but they all had the same shortcoming. The battery containers for CR2032 must always be opened with the proper side facing upwards, otherwise everything falls onto the floor. My battery cases for the CR2032 offer safe and clean storage without the cells falling out. In addition, you always have an overview of the number of batteries present.

The container is available in 2 versions, one for 10 and one for 22 button cells. The container consists of a drawer and a cover (container) and is safe against shocks and falls. The batteries are simply clicked into place and hold firmly in their drawer.

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Construction of battery container CR2032

The container must be stable and durable, but still have handy dimensions. In addition, each individual battery must sit firmly in its compartment and yet be easy to remove. I also asked myself how many batteries the battery container for the 2032 should actually contain. Most sets consist of 5, 6, 8 or 10, sometimes even 20. In any case, the container had to fit in my desk drawer. As I was not sure about the number of batteries to be stored, I decided on two variants, one with 10 pieces and one with 22 pieces.

The construction on the CAD starts with the drawer, i.e. the slide-in part, the long part for 22 pieces. The width of the drawer depends of course on the width of the battery, the battery is 3mm thick, 2.95mm to be exact, and needs enough air between the individual walls. A gap of 0.15-0.2mm for each side is enough to avoid friction. So if we add it all up, we get a shaft width of 3.3-3.4mm. We create the holding force that prevents the battery from falling out of the shaft with the edge trick. We create a circular pocket in the centre of the slot with a larger diameter than the battery. Then we cut off about 1 to 3 mm of the material above the centre point, thus creating an edge. This edge must be slightly smaller in absolute length than the diameter of the battery (in this case smaller than 20mm). If you now push the battery into the shaft, it must overcome the edge, which is also possible due to the elasticity of the material.

Now the battery sits in the shaft and cannot overcome the edge in the other direction with its own weight. This principle is actually quite simple, with the necessary knowledge about material, manufacturing tolerances, forces and holding torques. In the end, it was a mixture of experience and a few test prints until the optimum result was achieved. Now the battery fits neatly into the shaft and holds perfectly. And with gentle pressure, the battery can also be removed from the shaft again.

The next goal was to design the slot so that it holds securely in the case. This is also an interaction of material elasticity and the right diameter at the collar that holds the construction together. After a few test pressings, I was satisfied.

The shell of the CR2032 battery container is quickly constructed. Basically, it is a cylinder with a base. The inner diameter was adapted to the insertion size to ensure locking and the hole in the bottom of the sleeve is for air release, because when the insertion is pushed into the sleeve, the air must be able to escape.

Files for download

• Battery container CR2032

The post 3D printed battery container for CR2032 appeared first on Nerd Corner.

The flashlight was hard to position properly and it dazzled. For this reason, I came up with the idea of developing my own glare-free lamp, which you can simply place on the heating bed and is not blinding. Preferably wireless with a powerbank. I had already built my own powerbank with the Battery Shield V3, which I used as a basis this time.

This might also be interesting for you: Own powerbank with the Battery Shield V3

List of components

• 1 x Hollow socket 5,5×2,1
• 1 x Battery Shield V3
• 1 x LiPo 18650 3500mAh
• 1 x rocker switch 250V/3A mounting dimension 15×10,5mm
• 4 x hexagon socket head screws M2 x6
• 6 x raised countersunk head screws M2 x 20
• 17 x 5V SMD2835 LED strips
• 5 x jumper cable

Choice of LED

Since the basic housing of the powerbank with the Battery shield V3 was already finished, I mainly had to think about the lighting. LEDs with 5V or 3V should be used as illuminants, because the Battery shield V3 provides either 5V or 3V. For my purposes a lower lumen value is sufficient. After a short research I found suitable LED strips.

The light temperature of my LED strip is 6500K also called cold white. This light contains a lot of blue, which makes it easy to work with and details become visible quickly. Since the Battery shield V3 has three additional 5V and one USB A output, powering the LEDs is no problem.

The LEDs for the glare-free lamp are SMD2835. These are 2.5 mm wide and 3.5 mm long and have a slightly lower luminosity than a SMD5050. How much the LEDs consume is critical to the lamp’s burn time, as the power supply from the battery is limited.

Construction of the cover and middle cover

As already mentioned in the previous section, the base case of the powerbank is not changed. Instead, the LEDs are glued onto an inner cover. The middle cover also serves as a support for the hollow socket for the 3V output. Furthermore, a breakthrough was contructed to pass through the cables from the on-off switch. The slanted openings of the intermediate cover should help to apply adhesive to the LED strips from behind if necessary.

For the top side (the lid, where the light shines through) it became a little more complex. On the one hand, enough light should shine through, but on the other hand, it must not dazzle! Of course, a crystal clear lid would be ideal for the light yield, but as I said, then it would possibly dazzle. To strike a balance between effective light output and freedom from glare, several factors must be taken into account:

• Material selection (filament)
• Distance to the light source
• Thickness of the lens
• Printing strategy

The choice of material for the anti-glare lamp was “ivory”. The distance to the illuminant is 10.5 mm and the layer thickness (material thickness) is 1 mm. The layer height is 0.25 mm, i.e. one millimeter results in four layers, with the first layer applied 45° to the left and the second layer 45° to the right. Due to the different directions of the layers, the light is refracted again and again and becomes glare-free. This is a subjective perception and the designation glare-free therefore does not apply to all people.

Assembly

• Soldering the parts to the jumper cables:
  

• Cutting and gluing the LED strips: The LED strip is separated into two times 6 LEDs and once 5 LEDs and glued to the intermediate cover. The cable opening on the lid for the plug must remain free:
  

• Attach the hollow bushing to the intermediate cover:
  

• Screw the battery shield into the housing after the ten threads have been previously cut into the housing.

• Press the rocker switch into the cover:

• Press LiPo 18650 into the receptacle

• Connect cable and turn on:

• If all LEDs light up, place the middle cover on the housing and then place the cover on the middle cover and screw it down:
  

Glare free lamp CAD design

For the threads, the holes are designed for core hole diameter, i.e. for M2 for diameter 1.6 mm. You can tap the thread with the tap or form (press in) with a screw. Personally, I prefer the thread cutting. The two graphics show where the threads have to be cut on the housing.

Further notes

Some may wonder why the rocker switch sticks out of the lid and is not recessed. It makes it easier to turn the lamp on and off.  Most of the time you only have one hand free and can’t really reach into the recess, but if the rocker switch sticks out it’s easier to operate it. Nevertheless, I have also designed a version with recessed rocker switch, which you can download in the download section!

The power of the lamp is about 1.4 watts. At 5.05 V the current is therefore 0.27 A, which is no problem for the Battery Shield V3 and the LiPo. The burn time of the lamp is about 5 hours in continuous operation. For this data, I used a Samsung 18650 with 3500 mAh. The powerbank can be used in parallel to run the lamp. However, the total current should not exceed 3A.

I use this lamp not only for my 3D printer, but also for soldering, reading or as a night light. The powerbank is also extremely light with 127g.

Download files

• STL files of the glare free lamp

The post Glare free lamp and powerbank appeared first on Nerd Corner.

This might also be interesting for you: Development of a step-down module

List of components:

• 1x Battery Shield V3
• 1x LiPo 18650

Analysis of the Battery Shield V3

After the Battery Shield V3 arrived, the first thing I had to do was examine its properties in detail.  I thought about the tests beforehand and they were primarily based on my use cases. Since I am of course not a research institute, I kept the tests as simple as possible.

First, I tested the main function, which is charging a LiPo battery. The charging process on the module is indicated by a LED. Red means that the battery is charging and green signifies that charging is complete. Unfortunately, the LEDs are located on the bottom of the module and are therefore not easily visible.

According to the information provided by the manufacturer or the online retailer, the charging voltage is 4.2 V and the charging current is 500 mA. To verify these values, I measured and noted the state of charge of the inserted battery. The state of charge was approximately at 1100 mAh. The total capacity of the battery is 3000 mAh. It appears that the difference between fully charged and partially charged is 1900 mAh. To get the expected charging time, this value is divided by the 500 mA specified by the manufacturer. The calculated charging time is therefore 4 h. A standard power supply with 5V and 1A charging current is used as the power supply. In reality, the duration of charging was 4 h and 15 min. This is close to the theoretical value and thus okay.

Please note: Never use a brand new LiPo battery for this test, instead use one that already has some charge cycles completed. Otherwise, the result is not very meaningful.

Voltage testing in the Review Baterry Shield V3

In the second test, the different voltages provided by the module were examined. I divided this test into two phases. In the first phase (picture test 2_1) the module is used without a LiPo battery. Afterwards in the second phase a LiPo battery is used.

Of course, it is important to choose the right components to make the test as realistic as possible. For the USB-A connection I selected a load resistor with 1 A as well as with 2 A. This ceramic load resistor is ideal because a USB interface is available and the LED lights up green when 5 watts are consumed. At 10 watts the LED lights red.

For the 3 x 5 V outputs, I soldered 5V LED strips to two outputs and the third 5V output has a step-down module LM2596S which I constructed and set to 2V to power a 10 mm RGB Led. 3 V LEDs were soldered to each of the 3 x 3 V outputs. For this test a 5 V (18 Watt) power supply was used.

The module operating without LiPo battery

After connecting the consumers and the power supply, not much happened. Only the module-internal LED lit up red. Only when I deactivated the ceramic load resistor one of the 5 V LED strips and the RGB diode connected to the step-down (marked yellow in picture Test2_1) lit up.

Subsequent measurement of the outputs revealed the following values: A voltage of 3.24 V was measured for the 5 V outputs and 2.28 V for the 3 V outputs. The total current supply of the module without the LiPo battery inserted is about 11 mA. This should be sufficient for a small LED.

The module with LiPo battery

For phase 2 all consumers were removed and a LiPo battery (SAMSUNG INR18650-35E SDI KL59) was inserted into the module. As shown in the pictures, connectors were attached. This is because this module does not have a switch for the LiPo battery, so the load is immediately applied to the LiPo battery. It is simply uncomfortable to insert or plug in a battery under load.

All loads are in full mode in phase 2 and work fine. In addition, even the LiPo battery is charged. Questionable are the 4A amperage specifications of the 5V outputs. Given the amp numbers of the LiPo battery, this is possible, but it seems very high for a USB Micro supply. My recommendation would be to use the module with less than 4 amps.

Deep discharge protection

The third and last test is rather trivial. To test the deep discharge protection, only the ceramic load resistor with 5 watts was activated and no power supply was connected. This discharged the LiPo battery and if the deep discharge protection of the module terminates the discharge process on its own, the test was successful. This was the case. There was enough remaining capacity. However, such stress situations for the LiPo battery should still be avoided.

Casing for the Battery Shield V3

Of course I couldn’t resist to build a case for the Battery Shield V3 module. Beside the normal 5V USB output, which can be switched on and off by an extra switch, I also constructed a constant 3V output with a 5,5 x 2,1 socket into the case.

The housing can be downloaded in STL format at the end of the blog post.

Minor disadvantages

The On/OFF switch only switches the USB port. The 3 x 3 V and 3 x 5 V solder pins cannot be switched on and off by this switch.

For my electronic projects this disadvantage is not really dramatic, because I use mostly the USB port. Besides, additional switches can be soldered to the soldering points.

Downloading files:

• Datenblatt Battery Shield V3 (von AZ Delivery)
• STL Files for the housing

The post Review Battery Shield V3 – DIY Powerbank with LiPo 18650 appeared first on Nerd Corner.

This might also be interesting for you: Step-up module DC-DC LM2587S

List of components:

• 1 x hollow plug 5.5 x 2.1
• 1 x screw socket 5.5 x 2.1
• 2 x flat head screw M2x6
• 4 x raised countersunk head screw M2x10
• 1 x module LM2596S DC-DC Step Down

Implementation of the LM2596S step-down

For the step down converter, the DSN2596 was chosen because the module is cheap and widely used. To develop such a switching regulator by ourselves would take a disproportionate amount of time and money. Furthermore, the DSN2596 costs only a fraction of the price of the individual parts that would be needed for a self-developed switching regulator.

But be careful, some dealers sell DSN2596 modules that do not keep what they promise. It is important that the switching frequency of the LM2596 must not be below 150kHz. If you have an oscilloscope you can measure the ripple voltage at pin-2. The input voltage range is normally between 4 and 35 volts and the output voltage between 1.5 and 30 volts.

The output current is 2A without cooling and 3A with cooling. A heat sink should definitely be used and placed directly on the LM2596! For more than 2A output current, I prefer an XL4015, but this is rarely the case, as the 2A is usually sufficient. As always, the input voltage should be at least 1 Volt higher than the output voltage!

The efficiency of the module depends mainly on the difference between input voltage and output voltage. This means the higher the difference the more inefficient the module.

Construction of the case

The housing for the step-down module was developed analog to the housing of the LM2587S. The only differences are the mounting holes for the module and the position of the hole on the lid for adjusting the voltage via potentiometer. If you are interested in how such a case is constructed and what to consider, you can read more about it in the article about the LM2587S.

The following drawing shows how to assemble the case. It is not necessary to use the normal screws for this. The core holes for the M2 thread are also suitable for self-tapping screws. If you have an aversion to tapping or do not have an M2 tap available, you can also use other screws.

Download files

• STL files for the LM2596S
• STL files for the LM2596

The post Step-down Modul DC-DC LM2596S appeared first on Nerd Corner.

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List of components:

• Hollow plug 5.5 x 2.1 1 times
• Screw socket 5.5 x 2.1 1 times
• Flat head screw M2x6 2 times
• pan-head screw M2x10 4 times
• Module LM2587S DC-DC Step Up 1 time

Realization of the LM2587S step-up converter

A step-up module is needed. I decided to use a LM2587S DC-DC step-up module, because I already had it at home. Furthermore a plug for the socket at the battery and a socket for the power supply from the antique 24V power supply is needed. Plus some cable, screws and a case to protect the electronics.  All parts can be ordered easily, except for the case. This will be designed in CAD. For this, the parts that go into the housing must first be measured, since the official documentation and drawings of the parts are often faulty or not available at all!

Housing construction

When designing the housing, other questions arise such as:

• Should the housing be plugged directly to the battery or should there be a cable in between?
• Should the connector socket in the case or also be connected to the power supply through a cable?
• Do I need a fan (active) or are ventilation slots (passive) sufficient?
• Should I be able to adjust the voltage without opening the case?
• How big should the case be?
• Etc…

My solution was not to place any cables outside the case and not to use a fan. The size of my case should be about the same as a small powerbank with a 18650 battery. The circuit board should stand on columns inside the case. This has the advantage that the air can flow through better and the length of the thread is longer. By the way, an M2 thread should be sufficient because no large forces occur. The M2 thread is difficult to 3D print, so I cut it with a tap.

On the sides inside the case I left enough space for the cabling. In total only 4 cables are needed. For the socket that takes the plug from the power supply, I use a so-called bridge that stands on columns like the board. In this case the height of the bridge columns is the same as the columns of the PCB. With the bulges on the bridge I regulate constructively how far the socket stands in the housing.

The difficulty is to find the right center position, because the plugs are not all the same length. The lengths of the plugs differ partly up to 2mm! If you put the socket too deep into the housing, the holding mechanism of a short plug can’t grip and the cable including the plug slides out of the socket again. But if the socket is out of the housing, it can be damaged or scratch the surface on which the housing lies. In my experience, the socket should be recessed between 0.5 and 0.75mm in the housing. This is how I implemented it.

For the plug to the battery of my vacuum cleaner I use a standard rubberized screw plug. The challenge was to place this plug with guides in the housing and to press it down with the lid, so that the plug holds and does not wobble! I also planned threaded holes with M2 threads for the screw connection of the lid.

My three components were designed in CAD and then 3D printed. Soldering the electronic components is comparatively easy, because IN/OUT is already printed on the module. Unfortunately, I often confuse plus and minus on the socket, so I have included an illustration. Mostly here is outside minus and inside plus.

Measuring the voltage of the LM2587S step up

After successful assembly, the LM2587S boost converter is tested and adjusted to achieve the correct voltage (26V) for charging the battery. To measure, simply use a standard multimeter. The best way to adjust the measuring cables is to arrange the cables in a socket with glands. Then plug in the old power supply (23.5V output voltage) and turn the screw on the potentiometer counterclockwise through the hole with a small slotted screwdriver, always keeping an eye on the display. You have to turn the screw a few times to see the result on the display. When the desired voltage is reached, wait at least 15 minutes and readjust again. Mostly the voltage goes up by 0,3V-0,6V after a longer time. If nothing is hot but slightly warm and there is no unpleasant smell of burnt plastic, everything should be fine.

You can use this step-up module LM2587S for:

• Input voltage 3V-30V
• output voltage 4V-35V
• Output current max.5A

LM2587S step-up converter Remark:

• The output voltage should always be 1V higher than the input voltage.
• The input voltage should never be more than 30V
• The input current should be plenty higher than the output current

Download files

• STL files for the LM2587S step up

The post Step-up Modul DC-DC LM2587S appeared first on Nerd Corner.