This is a mini project showing how to build a small device helping you to find your lost keys. It’s working with Bluetooth low energy modules and utilizing ATiny MCU power saving capabilities. It can be also controlled from the mobile phone. I will give you an update as soon I get a Android 4.3+ phone.

Source code here:
To learn more about the Bluetooth modules I am using please watch this playlist:

UART code used from my MIDI device:

Stuff for the HM-10 modules can be found here:

IoT PCB considerations for Startups

Seeing that IoT products are so new, you would assume that getting an IoT printed circuit board (PCB) project off the ground starts by reinventing the wheel and finding your way through a wide range of technical complications. That is most certainly false.
But it doesn’t indicate IoT startups have a apparent method to stardom. Facing them is many different design and manufacturing factors which are unique to these small products. These points have to be factored in for the fresh new IoT product to be successful.

On the plus side, it’s very important for IoT startups to recognise that the basic foundation for a successful awesome product exists. This suggests experience and knowledge relating to the design, fabrication and assembly of these advanced products are obtainable. Also, the best advice is for prudent IoT product business owners and leaders to heed the counsel that expert electronics manufacturing services or EMS providers offer. These businesses as well as their engineering employees have previously performed this work with pioneering IoT corporations in Silicon Valley joining the initial phases of this coming market.

The PCB of an IoT product is a special beast than the traditional one, which is much larger and flat. IoT devices, in contrast, consist generally of either rigid-flex or flex circuit assemblies, which include their very own groups of design layout, fabrication and assembly points and subtleties.


A top consideration is to hunt for knowledgeable designers who’ve undertaken a large amount of rigid-flex PCB designs. PCB space for an IoT product is tight. So you want the designer to have direct layout practical experience to properly design crucial elements on that compact room.

Even, most IoT gadgets are not stationary; they have considerable movement and rotating. Here, the knowledgeable designer plays a significant role in figuring out bend ratios and lifecycle iterations as a critical part of a design. Additional crucial design layout points contain signal trace thickness, number of rigid and flex circuit layers, copper weight and stiffener placement. Stiffeners are employed on flex circuits to make sure that elements attached to the flex circuit stay closely in position to stay away from movement.

One other focus is through-hole component positioning in rigid-flex circuits. How come is that key? Many of IoT items are founded upon surface mount device placement. Nevertheless , there could be through-hole elements, which are normally attached to either the rigid portion or the flex portion of the board. Through-hole elements are usually useful to connect input/output or I/O signals to the exterior world. That way, those signals can show up having an LCD or LED monitor. Through-hole component placement is a crucial account in an IoT device considering that when applied to the flex part of the board, suitable stiffeners should be designed and used for appropriate assembly.

And finally in the layout category, the high temperature which elements bring in has to be considered. IoT gadgets are starting to be more sophisticated with rigid-flex and flex circuits featuring approximately 12 to 14 layers. A few gadgets are digital. Nevertheless , increasingly more analog products are being employed in IoT products. Analog circuitry results in considerably more heat than digital ones. This suggests heat expansion plus contraction rate ought to be taken into account. In tech lingo, this is generally known as the Coefficient of Thermal Expansion or CTE and the right handling of it.


Choosing the right fabricator is critical and is linked to the EMS enterprise you have selected. The fabricator you would like needs to have IoT PCB fabrication experience. Amongst crucial points here are insuring good adhesions between layers on both rigid and flex circuit sides, realizing all the essential calculations and obtaining a robust comprehension of when current moves from the rigid side to the flex side.

These fabricators also must possess an in-depth comprehension of remarkably tiny parts for instance 0201 and 00105 device packages, package-on-package, and the employment of fine-pitch ball-grid array or BGA packaged devices.

Furthermore, they should have experience with designing boards with fairly tight tolerances in terms of footprint for those types of BGA devices, in terms of up-to-date capabilities like laser direct imaging for putting the solder mask on the board. They need to have laser drills for via drilling with sizes of 5 mils or under since these IoT products could be so modest that a standard drill size of 5 to 8 mils probably won’t be all you need. They may require to go to a 3 mil, which indicates that you must have an innovative laser drilling capability indoors.

If you’re placing via-in-pad, it is a easy way to utilize the small land that’s available on the rigid-flex board, but it creates trouble for assembly. If vias aren’t fully planar or flat in shape, it might be an issue through the assembly of those tiny BGA packaged devices. That’s because non-planar surfaces can threaten the integrity of solder joints.

Occasionally via in pads leave bumps in the event they’re not scrubbed the appropriate way after putting the vias and gold finish at the top. In cases where there are bumps, then the solder joints in the assembly for those tiny BGA balls in those IoT devices wouldn’t be a great joint. This could create irregular connections, which can be a bigger issue to cope with and take care of. It all boils down to which EMS enterprise you are using because they’re the ones who will choose the fabrication house to make a thriving IoT product for you.

PCB Assembly

It’s crucial to head off to knowledgeable EMS companies that have successfully assembled IoT and wearable PCBs as they have specialized tooling and fixtures readily available, which are essential for assembly to make certain that components are placed correctly, exactly and the printing is performed appropriately.

Printing can sometimes be a difficult task for IoT products. If it’s a rigid-flex board, then there’s a change between thicknesses of the rigid and flex circuit portions, which means a special fixture is necessary to keep the complete rigid-flex board planar or entirely flat to enable effective printing to become carried out.

Startups really should be well prepared to pick the most suitable manufacturing partners and EMS companies. This way they can assure they have got enough experience in advance to get the multitude of design, fabrication and assembly details effectively performed since they are key to a victorious and prompt IoT product roll-out.