The sotware is adapted in many ways.
First of al another method is emplemented to determine the distance between XBee modules. To provide more reliable data, it takes multiple samples of the signal strength. After taking these samples, a mean value is calculated. The next step is looking in which interval the mean value appears. This interval is compared to the present interval. If the interval doesn’t change with the current interval, the frequency of the blink is not adapted. When it does change and when the next mean value(s) lie(s) also in another interval, the frequency is adapted to the new interval. This ensures more represantative frequency in function of the distance. Beforehand, there were bad transitions between the frequency values.
A second adaption is the configuration of the XBee. This is done using the AT command. To configure the wristband, a number is needed that represents the interests of the user. In the setup of the Arduino UNO, a check is done if the XBee is setted by looking in the EEPROM momory. If an address is stored, it means that the XBee is configured before. If not, the UNO waits till it gets a number through serial communication. When received, the UNO will configure the settings of the XBee and save the number in the EEPROM memory.
The colour of the wristband represents the favorite stage of the user. An XBee is used at each stage that sends a broadcast message to all XBees in the neighbourhood. This message contains RGB values. Each stage has one colour. When receiving a stage message, the micro controller count the amount of times the color is received. The colour that is received the most, will be visible as the colour of the wristband.
The XBee module is one of the most power consuming units that is used. Therefore, it’s beter to use the sleep mode of the XBee to extend the wristbands lifetime. There are multiple sleep modes available. The ‘Pin Hibernate’ mode is used and reduces the power to less than 10µA in sleep mode. Its programmed that the XBee sleeps the same amount of time that its awake. The mean power consumption of the XBee is therefore halved from 50mA to around 25mA.
Two XBee modules can communicate with eachother. Leds can indicate the distance between the two modules. The Xbee’s are placed on a shield for Arduino UNO. The microprocessor with shield is too big to use it in a watch/bracelet. Therefore, the same functions can be programmed with an Arduino Micro. There are no shields for the micro to plug in the XBee. A print layout is made to connect the XBee and the processor to eachother. This was needed, because the XBee modules pitch is 2mm, wich is less than the standard value of 2.54 mm. A battery is not included yet, because we are not sure what leds etc we want to use.
The print is handed in:
This week we mainly made test to get the best light. The prototypes we made last week are stil to big but we could already test the light with the silicone, plexi, tubes,…
As you can see the tests with the silicone are the best, so we decided to produce our bracelet with silicone. But because the silicone is fully transparant the light reflection isn’t at his best. We made a new prototype with a transparant stroke in the middle and white silicone at the outside to increase light reflection. This will probably give a better result. For next week we are designing a thinner, elegant bracelett. To see how the bracelett will look like in actual form.
At first we wanted to see what the effect was when we bend the plexiglass. To see how the light diffuses.
The effect is visible during the day and at night. During the day it depends of the position towards the material. If you see it from the side: you can see the light, if you look straight towards the material, you can’t. In the dark the effect is really good.
We used the laser cutter to see what the effect was on the engraved parts. As expected,
the light follows the engraving.
Because we saw some nice diffuse light effects in the silicone mold. We wanted to create a bracelet like this: for the connection methode, looks, size and light effect.
We created a mold for the bracelet. We made 2holes: 1 for the electronics and 1 for the connection. (like a bycicle light- We embedded a light to see how it looks.
The LED’s embedded in the bracelet don’t really work. they are not strong enough.
when we put LED’s underneath the bracelet: the effect is like this. (stronger LED’s)
We want to be able to create a wristband with a diffuse light effect. There are several ways to create light. We did research about the following types of light.
- Optic Fibres
- Led embedded in silicone wristband
- Glow in the dark
- EL tape
- Etsing in plexiglas
We have tried several techniques to see what the effect was.
Light trough silicone mold –> diffuse effect
scratching on plexi glass –> not so visible during the day, nice effect with light.
Hollow tube (hard material) –> nice diffusion, hard material
Previous time, a RF component was used to try calculating the (relative) distance between two Arduinos. These components didn’t have any possibilities to measure the signal strength (RSSI). Neither did the Bluetooth module (HC-06). A ping-based algorithm didn’t provide useful data: the range of the obtained values wasn’t big enough. An alternative is to use a XBee module. XBee is a radio module that offers a lot of features. The one we’re interested in, was the possibility to measure the signal strength. After testing the modules, the measured data seemed good enough to get a relative distance between two Xbees. A test environment is made to use the measured signal strenth as an indicator of the freaquency of a led. The result can be seen in this video.
Note: the freaquency is not adapted for bigger ranges yet. It’s now set to see the principle behind it.