Electronics development. Project audit in examples. We save the warm floors with all the habr

I have long wanted to conduct a detailed analysis of a project for the development of electronics, to show obvious errors and the right approaches that will help to eliminate them. Perhaps it would have been going for a long time, but the case turned up - a post on the Habra blogosphere “The formation of a thermostat. How did it happen . ” The article caused a storm in the comments , including from my side , which means the topic is relevant. What is the point of talking about projects that have failed and sunk into oblivion, where nothing can already be fixed, is it not better to try to do a good deed?



Let's try to audit the project taking into account the most valuable comments and hope that the team will extract something useful from it. We take for the minimum viable version (MVP) the information that the authors disclosed in their article and think about how to improve it during the next iteration.

A bit of circuitry

The materials laid out in the article contain too little information on the basis of which one can conduct a qualitative analysis of circuitry and circuit boards. Perhaps we were generally presented with outdated board options. But even if this is so, the analysis will be useful not so much for the authors of the project as for the readers.







With a high degree of probability, it can be argued that the frequent “hangs” of the ESP module are associated not so much with its “glitchiness” as with serious problems in the power supply system. An attempt to get out of the situation by introducing an external dog, is similar to treating a patient with fever by immersion in a bath of cold water. In the short term, the result will be achieved, but such treatment will most likely end in death.



Small-sized high-quality AC-DC modules from well-known manufacturers cost a lot of money and “undermine” the economics of such projects even more than “sophisticated” graphic indicators with a touch screen. You can understand why it is difficult for novice developers to overcome the temptation to develop a switching power supply independently and quickly. In DIY projects, such attempts often end in a light, but long memorable, electric shock and a small firework. To risk in a similar way in commercial development is too dangerous and in this case I consider the installation of a purchased module justified, but the question of its choice remains open.







In this project, we are dealing with an extreme case - an inexpensive, small-sized, reliable power source is needed for the controller. But most importantly, it should provide suppression of significant impulse noise caused by relay switching of high power loads. There is a wide selection of AC-DC power supply modules on the market, the passport data of which are very similar, and the price is different at times. There is every reason to believe that not only due to brand margins.







A visual study of the insides of the cheapest of the three modules shows that a large number of manual operations were used to create it. This reduces the repeatability of installation and increases the likelihood of marriage. You can “lay” such modules into the specification of a serial product only after thorough testing of several copies from different lots, reverse engineering and analysis of circuitry. In addition, one hundred percent control will be required before installation, and you won’t get away with simply measuring the output voltage. We will have to create an automated stand for 100% control of these products under load and in the condition of impulse noise. So, choosing an extremely cheap option, you need to weigh everything seven times.





It's time to take a closer look at the photos of the boards laid out by the author.



Even in the scant documentation we have at our disposal, there is food for analysis.









We will not find fault with the choice of the type of interface connector, because we have a prototype, and I'm sure that in the real device there will be something more reliable. The location on the board and the very presence of a temperature sensor inside the housing are more likely a place to install it , perhaps with its help the design author intends to measure the temperature inside the housing. Why, for me it remains a mystery.



Much more disturbing is my right photo, which shows design elements of high-voltage high-current circuits.



For comparison, below are photos of the insides of the popular Chinese Sonoff wireless relay module, controlled via WiFi, with a sub-GHz submodule on board.







The miracle of price optimization in China seems more prepared for operation and certification than our “defendant”. In it, one thing confuses me - the terminal block is too small in size for currents of 10 amperes. But the Chinese device is optimized in performance for switching lighting. But “ours”, by definition, should work with high currents, for which it has a relay of as much as 16 Amps. I hope that the relay is selected to the proper quality and its contacts will not “stick” after a couple of months of operation, but as for the long and happy operation of the terminal block at such currents, I have serious doubts, although the copper conductors inserted into it must be the minimum diameter (1.5 mm) most likely it will work out. Personally, I, at least for high-current circuits, would have hammered into the specification the terminal blocks of a well-established manufacturer, for example, WAGO or Weidmüller, which is a very important part that you should not save on. Having carefully looked, you can see the tricky cuts in the Chinese version (number 2). If the author of domestic design believes that they are needed for weight loss, then he is deeply mistaken. They prevent carbonization of the section of the board between two printed conductors with a large potential difference due to breakdown. Breakdown is an extremely unpleasant thing. It is good if one of the tracks or a fuse simply burns out due to the arcing of an electric arc. And if a fire starts? Especially often, such troubles occur in high-voltage DC circuits - between them, due to the polarization effect, dust likes to accumulate, and with increased humidity ...



The only significant detail on which our Chinese partners allowed themselves to save is the capacitor, the role of which is to suppress pulsed interference.











We will not go deep into details, we only note that for this it is worth using specially designed capacitors that can absorb short surges with voltages up to 2500 Volts. Those intended for domestic use are marked X2.



As a rule, when such capacitors fail, a short circuit occurs between them. In the circuit, the current rises sharply and either the fuse or the inductor burns, which often put the fuse in place. As a result, the device, which has become dangerous to human life, goes out of operation.



If you decide to use more low-cost capacitors that do not contain such a marking, you must make sure that the maximum allowable voltage on them is at least 600 volts and they are suitable for operation in pulsed circuits, like the one on the right.

Let us return to the published section of the floor heating controller circuit.







It seems that there is also a capacitor for suppressing impulse noise and the AC-DC module is similar to galvanically isolated ... Unfortunately, we are not able to see what is hidden under the top board. There probably should be an AC-DC module, but you can only guess about the type of left capacitor in the circuit. If it is chosen incorrectly, then the abundance of electrolytes is not able to provide the required level of suppression of impulse noise, and this, in turn, can most negatively affect the stability of the WiFi module.

With this, by force, I finish the story about circuitry and move on to a more important topic, for which the article was written - product development and marketing.

Talk about the eternal - values

So, you conceived your product. I hope it has unique properties. The more significant these differences are, the more seriously you stand out from the competition, which means you attract attention. But there is one caveat. Differences can both attract new customers and repel.



Suppose you invented a bucket in which the bottom is full of holes. Most people use a bucket to carry and store liquids. Their purchase of your innovative bucket will infuriate you. But there is a man who guesses to use it in order to sift sand from stones or as a shower. He will be very pleased with the presence of holes. The problem is that it will be only one buyer per 1000, or maybe 10000, those who use buckets for their traditional purpose.



We draw conclusions: In the process of product development, functionality does not make sense in isolation from the audience of users for whom it is of value. For this reason, at the earliest stages, you should determine the circle of consumers for whom your device may be useful. It is necessary to approach this with special care - to find out their addictions, way of thinking, property status and most importantly, how important your problem can be for your product to help solve it and why it does it better than existing ones.

Consumer analysis. Budget sector

Let's try to outline the circle of potential consumers of our thermostat and the trends that affect their change.



In the private sector, it’s a little expensive to heat electricity, so the first thing we are interested in is buyers of new apartments and secondary real estate. It is easiest to make money in a growing market, but today we have the opposite picture.





It is not necessary to count on recipients of mortgages with a minimum initial payment. In conditions of falling incomes, they are not up to “warm floors”.



In the budget segment, we have no one to catch, we turn our eyes to the middle class.

Consumer analysis. Middle class

Despite the fact that the size of the middle class is decreasing, due to its re-segmentation, the replacement of entrepreneurs with officials, ministers of worship and law enforcement agencies, there should be a certain flow of clients interested in installing warm floors. Against the background of a general decline in income, this segment is also being replenished by IT specialists, whose salaries continue to grow in ruble terms due to the high convertibility of their specialties in foreign markets. And this is good news.

Consumer analysis. Elite demand

It existed and will exist in our country, well, at least until the oil runs out. However, there is every reason to believe that the patriotic attitude of the majority of representatives of this group weakly stimulates demand for the products of novice Russian entrepreneurs in the field of home life support systems. With a high degree of probability, they will turn their eyes to well-known Western brands in the upper price range, at least for reasons of prestige.

Consumer analysis. To summarize

1. The fastest growing segment Supernova middle Russians - a growing segment of the middle class - officials, employees of power structures of all stripes, clergy.
2. Slowly growing segment Highly qualified specialists, primarily in the field of
3. Falling demand Small and partly medium-sized entrepreneurs.

We build value hypotheses

The first segment has the most solvent demand, part of which can be competed by competing with well-known western brands. When organizing sales, it should be borne in mind that this is a very specific audience. Products sold to her should have the following qualities: expressive and diverse design. People who “raise” their status quickly, with extremely high self-esteem, can have the most unexpected “ideas about the beautiful” and are ready to pay for their implementation. The ability to customize their appearance is important to them to a large extent. The interface must be as simple as possible, designed to switch several preset modes. Unusual features are appreciated. Reliability of work and the fastest level of service is very important, otherwise you can get very big troubles instead of profit.

The second segment is ready to pay primarily for high functionality, even if it never takes advantage of it. For IT professionals, software flexibility and the availability of an open API for integration with smart home systems from other manufacturers will be a big advantage.



Third segment For the most part pragmatics. First of all, good basic functionality with default settings, ease of management and design that fit into the “calm” interior of the room are important.

Looking for competitive advantages

If you do not have competitive advantages, then the costly operation of creating a new product does not make the slightest sense. Buy existing devices on the market and focus on sales and software development for them.



To find additional competitive advantages, you can try to use a scientific approach. There is an excellent technique based on building a “strategic canvas”. The book “The Blue Ocean Strategy” is devoted to this technique, and an example of its application to determine the functionality of a new electronic product can be found in one of my previous articles on Habr.



Within this article, there is not enough time for a full-fledged study, so we will be guided by the logic, experience and valuable advice prompted in the comments.



Based on the circle of consumers that we have identified for ourselves, it becomes clear that there is no point in trying to fight for a super-budget niche - there is weak, and most importantly falling, solvent demand. Leave it to the Chinese magicians and will think further.



The most demanding consumer qualities of the product are the buyers of the first segment. We will focus on them in the first place. What is needed in order to satisfy them:

• The most simple user interface
• Several operating modes for the most standard cases with carefully thought-out default settings
• “Solid appearance”, which at the same time is unusual and can be customized for the user.
• Extremely reliable operation even in conditions of a significant deviation of the mains voltage from the nominal value and serious interference caused by poor quality wiring. Any failure of equipment from such customers is fraught with very big troubles.

The product qualities described above will not be superfluous also for conditional “IT employees”. However, they can be presented with an additional serious bun in the form of an open API, with the help of which they can realize their fantasies in controlling the device and combine it with the components of their “smart home” that already exist in them.



How to realize all this?



What to do with appearance? We’ll make 10 housing options and pay 5 kiloevs for each mold, print 500 thousand cases of different shades and sell them before the loan day?



Not the best solution



And why not ask for help from the Auditorium? .. If you carefully read the comments on the article, then on the basis of only two you can get recommendations for solving the problem. At least for the next iteration.



So, the top 1 in my ranking is a comment from a respected lingvo.



He deserves to be quoted verbatim.







The second most valuable comment from the no less worthy zapimir habrayuzer and it is located very close.







Of great value is another excerpt from the commentary of the same habrozer.







Only two people were able to tell us the way, which is worth moving!

Let's try, taking into account their comments, to create a new iteration of the device concept.

Divide and rule

Wireless Modules

The main change - we switch to a distributed system - we divide the device into parts, combining them with a wireless interface.



The right choice of interface type and radio frequency range is the cornerstone task on which the success of a project depends.



At first glance, the sub-gigahertz range of 868 MHz is the best solution. Waves of this frequency are much lighter than their higher frequency counterparts, overcome the obstacles of propagation in the form of drywall panels and even reinforced concrete floors. In addition, today, in this range, there are much fewer devices than at 2.4 GHz.



However, I would opt for transceivers with support for Bluetooth Low Energy (BLE), which operate in the 2.4 GHz band. This range is heavier loaded, however, this solution has many serious advantages:

• The number of working channels is much higher
• The BLE standard has mechanisms for automatically “jumping” from channel to channel to offset interference
• In the fifth version of the protocol, support for distributed self-organizing MESH networks appeared, which allows building additional heating control systems not only within large-area apartments, but also in cottages without additional network extenders
• The BLE standard is ideal for creating sensors and other extremely low-power devices that can run on the same battery pack for several years.
• If necessary, modules with increased power sensitivity can be used.

It makes no sense to independently design a wireless communication channel - with small volumes of purchases, the equipment will cost more than the purchase of ready-made modules of decent manufacturers. Moreover, having no experience with RF components and specialized measuring equipment, it is difficult to count on a good result.

Wireless relay

We control the contact groups of the “underfloor heating” relay with a separate device that does not have its own display and controls. It is carried out in the standard purchase case. At the first stage, it is worth considering the feasibility of using a fully ready-made commercially available device. In the future, upon reaching serious volumes, it is possible to develop your own, designed taking into account operating experience during initial sales.



The supplier must be selected carefully, preferably already having a Russian certificate.



At the initial stages, it is possible to use a purchased wireless electronic relay module, but it is necessary to approach its selection and testing with great care. The main plus of this decision is that you don’t have to spend money on developing a power source and certification. The second - for the troubles associated with high voltage and current circuits, the manufacturer of the purchased device is responsible. It is advisable to find a device that has the same wireless chip on board that is taken as the basis of the project. It will be possible to reflash it with your code.

Sensors

Modern BLE chips are based on microcontrollers with an ARM4 core and have a rich enough periphery for implementing various sensors and more complex devices without the use of an additional microcontroller.



To create wireless sensors, you need to add to the board with the BLE module one of the sensor chips that can measure temperature and pressure, for example, as I described in a previous article on Habr.



In order for such a device to work autonomously for several years, one three-volt CR2032 battery is enough.



To save money, several types of sensors can be bred on one board at once and, if necessary, installed on one board or another peripheral.

• humidity / temperature sensor
• leak detector
• contact sensor
• inertial sensor

Hub

BLE is good, but it doesn’t provide Internet access. We’ll have to think about a hub that will become a bridge between BLE and WiFi. There are probably not many options here. WiFi based on any of the ESP modules, better than the modern type of ESP32. BLE module, in addition to performing basic functions, can monitor the correct operation of the WiFi module and reboot it if necessary. Theoretically, the latest generation ESP 32 chip can work both in WiFi mode and in BLE mode, but I would not risk making a router solely on its basis.



The device receives power through a microUSB (USB3 typeC) connector, has a built-in battery for autonomous operation, a sound emitter for warning of an emergency and a seven-segment LED emitter for several discharges, hidden under the frosted glass.

Design Details

Let's try to save on the case. This will be extremely useful when organizing the first sales in small batches. It can be done in a fashionable now minimalist design - in the form of a puck. The base of the ring, which is obtained by cutting like a sausage tube. We install a translucent plastic cover on top. Below is the second cover, to which, for devices whose location it is often supposed to be changed , magnetic rubber can be glued, for stationary double-sided tape.



Xiaomi sensors are similar, but much more complicated. With their production volumes, making a molding for the manufacture of the upper part of the body of complex shape is not a problem.







All devices except the relay module can be executed in this form factor. At the first stage there will be enough cases of two sizes. More for hubs, less for sensors.



Such a case is good in that, having a stylish appearance, it is very easy to manufacture in small batches and for customization. You do not need any 5000 USD per mold. Tube cutting is a simple and cheap operation, cutting plastic sheets as well.

HOW TO SATISFY EVERYTHING AND IMMEDIATELY

Each star has its own piece of heaven,

Each sea has a sip of rain.

Each apple has a place to fall,

Each thief has an opportunity to steal,

Each dog has a stick and bone,

And each wolf has teeth and anger



As a result of our research, we got the concept of a convenient and flexible device. There is only one problem - we’ll enter the market late in the day. Today, not only nameless Chinese firms, but also global corporations are following the same path. One of the most serious competitors is the brainchild of Philips - a series of devices manufactured under the common brand “Xiaomi”. To compete with them, one must look for serious advantages.



A company with low resources entering a falling market does not have many trump cards up its sleeve. It is necessary to concentrate on related services and a simple installation procedure.

Boxed versions for budget buyers

The ability to choose from several standard versions in which:

• the supplied devices are already connected to each other. Take it out of the box and get started
• well thought out several default configurations to choose from
• all you need to do to work with the boxed version is to download and install the mobile application, go to the server at the specified address, scan the barcode on the box and enter the password. After that, you find yourself on a profile that is already configured under the devices in your box and select one of the operation scenarios.
• “ ”
• , , ,

,

• , ,
• . :
• the manufacture of linings from non-standard materials, up to semiprecious stones (for this, you can involve craftsmen from service rendering services, for example, from profi.ru
• Sales option with installation and configuration. Installation can be combined with delivery, and can be performed separately. Here you need to weigh the pros and cons.

IT specialists

Since among the clients we specially singled out those who are familiar with IT technologies firsthand, we will prepare buns for them. This is of course an open API with great features for customization and integration into other systems.

Third-Party IOT Projects

If the project is successful, an open API and assistance in customization can attract developers of individual devices in the field of IOT, who fully reveal their capabilities as part of complete systems.

Time to take stock

Our small study strongly resembles a brainstorm, which resulted in a host of hypotheses awaiting verification. It will be extremely difficult for start-ups to develop simultaneously in all the areas outlined, therefore it will be necessary to choose the most promising ones, test, switch to others ...



In conditions of extremely limited resources, in weakly growing or falling markets, this is also difficult with purely software startups, and in the case of a hardware product almost impossible. Creating a commodity device on your own savings is extremely difficult even with a unique idea.



The size of the article did not allow us to discuss possible steps that need to be taken for promotion and PR. Hopes solely on word of mouth in most cases are completely unfounded.



Perhaps I will touch upon these problems next time if the article arouses interest ...

Instead of an afterword

If you have done what no one has done before you, then perhaps you are a Genius. But much more often the reason is more prosaic - just anyone but you does not need it. Large companies spend millions of dollars studying demand. A similar reaction to free comments and suggestions from the target audience is nonsense.



You must be able to separate flies from cutlets. If you do something solely for the sake of getting high, it is certainly commendable. Only this is called the word DIY and is not always scaled as part of a startup.



If you are developing a device as part of a commercial project, it should be borne in mind that creating a successful product without feedback from potential customers and experts is almost impossible. In today's world, the one who knows how to use it in the best way is on a horse.



A huge request to read to the end to complete the survey