Limiting speed on urban roads to decrease accident rates

The majority of the population now lives in urban areas. It is estimated that up to 75% of Europeans, 81% of Latin Americans and more than 82% of North Americans now live in cities. Although the number of accidents is not directly linked to the number of inhabitants of a city, the fact is that the majority of road accidents occur in urban environments.

30 mph speed limit sign.
30 mph traffic signal. By Salah Ait Mokhtar.

In accidents occurring on urban roads, it is also more common for other road users to be involved in addition to the drivers and their passengers. The worst off, as always, are pedestrians and cyclists. To try to reduce these figures, one of the easiest and least expensive measures to be implemented by administrations is limiting the speed of motor vehicles within the urban area. By limiting its speed the safety of all road users is significantly improved.


Add a solar panel to your Arduino projects

One of the possible extensions for Bike Pixel that I am considering is to add a module that allows charging its battery through a solar panel. In theory we can power our Arduino projects by directly connecting a solar panel. If we have some current stabilizer circuit and a lot of sun radiating the panel there should be no problem. But as soon as the energy supplied by the light is insufficient our device will stop working.

Picture of a photovoltaic solar panel.
Picture of a solar panel on a roof taken during my vacations.

State of Open Source Hardware 2021 report presented

After the shutdown of the Open Source Hardware data organisation (OSHdata) in April this year, it seemed that their activity quantifying the development of the Open Hardware community had come to an end. Fortunately, the Open Source Hardware Association (OSHWA) has, in part, taken over the legacy of OSHdata. A few days ago they presented a new report on the state of Open Source Hardware. In it they show different statistics and interesting information with the current state (as of 1 July) of the community. Last year’s report produced by OSHdata focused more on the commercialisation of open hardware projects. This year’s report is dedicated to the community and the effects of free hardware on its members. Below is a summary of the highlights.

Expermients with electronics and sound. Image by Chris Obrist from Unsplash.

Just wear a helmet

Even more important than a good bicycle light (eg. a Bike Pixel 😉 ) a cycling helmet should be the basic security measure to wear when we are riding on bike. This is especially true in urban, leisure or commuting trips. In such cases speeds are lower (including ours and the other vehicles that surround us). Therefore, in the event of an accident, the impact energy is much lower. On the other side, helmet may be less useful on the road, where a running over vehicle (cars, trucks or trains) goes at higher speeds than 90 km/h. In any case wearing helmets always reduce mortality and morbidity of cyclist trauma.

Even Darth Vader wears his helmet while riding a bicycle. You also should!
May the helmet be with you. Photo by Daniel Cheung.

Using Arduino Pro Mini on your projects

If in any of your projects you have limits in terms of space or power consumption one of the best solutions is to work with an Arduino Pro Mini board. The USB port and the programmer circuitry have been removed from the design. As a result, its dimensions are considerably reduced. That’s why for the new version of Bike Pixel I’m thinking of using one of these boards.

Image of an official Arduino Pro Mini board.
Oficial Arduino Pro Mini board (by sparkfun)

There are currently two versions of the Pro Mini plates. It is possible to find them in 3.3V with a processor at 8MHz and with 5V at 16MHz. In both cases, apart from reducing their size, they use less energy than their big brothers (especially in the case of the 3.3V version).


Report on the state of the Open Hardware

The Open Source Hardware data (OSHdata) organization has presented an interesting report on the current state of open hardware. The report presents statistics on different aspects of all the projects that have been certified. By February 2020 (date of the analysis) there were already more than 400 projects. Among others, the authors of the report include data on the commercialization of the projects, information on their creators or the licenses used. The full report is available on the report page of the OSHdata website. Below we present the most interesting ones.

Illustration of the design process of Open Hardware projects.
Open Hardware design process. Autor Nicolas Thomas


One of the key aspects highlighted in the report is the commercialization of open hardware projects. Among more than 400 projects, almost 60% of them currently offer the products developed for sale. In addition, the average price of sale of the products is $211.47 being the price of more than half of them lower than $35. In this first price range you can find products such as sensors, 3D printed parts and USB accessories.

Statistical charts of commercialized Open Hardware products. Percentage of products marketed and sales prices.
Commercialization of Open Hardware projects. Marketed products and its price ranges.

Creating your custom parts for Fritzing

Fritzing is one of the best circuit design and documentation tools. It has a large component base and there are many community-created parts. Even so, sometimes we will not have available some of the ones we want to integrate in our projects. In these cases, creating our own custom parts for Fritzing allows us to add new components based on our own designs.

Right now I’m working on the design of the front version of Bike Pixel. During its design I used several new components such as vertical touch buttons. These are not available in the application and therefore I had to create my own components. Their diagram is shown in the following image:

Design and measurements of the vertical push button developed during the tutorial to show how is the process of creating custom parts for Fritzing.
Sketch of the vertical touch button.

Bike Pixel user manual and main features

The first prototype of Bike Pixel has been ready for some time. Its use is very simple and only it is necessary plug it into a power bank to get it up and running. Even so, it would not hurt to present a small user manual and its main features. The Rear model includes a USB port and three buttons as shown in the following image:

Functions of the buttons of the Bike Pixel Rear

How to add a LiPo battery in our Arduino projects

In the next Bike Pixels version I want to integrate a rechargeable battery so you don’t have to rely on an external power source. In principle, this might seem trivial, but it’s not. Lithium-polymer batteries (or LiPo) are dangerous if they are incorrectly charged, overcharged, overheated or stored incorrectly they can explode. Luckily to make things easier for us and allow us to use a LiPo battery in our Arduino projects we have several modules that can do some of the work for us. One of these modules is the TP4056.

TP4056 module specs

The main element of the module is the TP4056 chip itself. This chip is a programmable linear current and constant voltage charger for single cell LiPo batteries. The module also integrates two LED indicators of the state of charge and two additional chips in charge of the protection of the battery. Although there are versions of the module that do not have these chips, in this case we will use a version that does have these elements like the one described in the image.

TP4056 module Components
TP4056 module main components description.

The module performs the charging process. First it ensures a constant current until the LiPo battery reaches 4.2V. Then, it gradually reduces the charging intensity until the battery is fully charged and ends the charging cycle when the charging current drops to one tenth of the programmed value. It supports input voltages up to 8V so it can be used directly connected to a USB port or a mobile charger up to 1.2A.


Advantages and disadvantages of Arduino clones

One of the first things we should do when we start a new Arduino project is to look for a free board. Then we have to disconnect what we had on the board to make room for the new development. Of course, the ideal would be to have a couple of dozen Arduino boards, but that would cost us a small fortune. Luckily we have the possibility of using Arduino clones although these have some advantages and disadvantages.

Arduino Nano original and its clones.
Original Arduino Nano (left) along with two clones. The middle model is the one that includes the first prototype of Bike Pixel Rear. The one on the right is totally modified being all the elements on one side so it is the least thick.

During the project I used both original plates and clones. In testing and developing the prototype, I used an original Arduino UNO board and a Nano. For the final assembly of the prototype I opted for a clone, directly soldering the connections and components over it. This choice was due to the fact that the original Nano plates include by default welded legs. In our case this was the first advantage of the clone board but can be also a disadvantage as the welded legs facilitates the connection with other elements and we can do without the welder.