Group Actions
Engagement
  • Author Author: balearicdynamics
  • Date Created: Date Created
  • Views 1547 views
  • Likes 8 likes
  • Comments 17 comments
Related
Recommended

Meditech: Prototype assembly essentials

balearicdynamics

Introduction

At the actual date the first part of the project is closed: machines are assembled in the box, powered and the entire architecture has been set about 95% accordingly with the initial design. The only plus is the introduction of a fourth PI as the Cirrus audio board it is very difficult to match with any other hardware implementation on the same device so the PI hosting the Cirrus will only work in conjunction with the Bitscope module via the USB that is used in reverse mode. I mean as an acquisition and pre-processing probe instead of its traditional role of analog and logic analyser.

 

A note on the power supply

As mentioned before in this first experimental device Medtiech will be powered by an external ATX source providing 3.3V, 5V and 12V distributed with a simple set of power replication units as shown in the images below: the first shows the ATX connected to the main logic power supply switch while the second shows the simple circuit of the power replicators distributed along the center of the box to reach easily the devices..

 

TODO: Analyse in-depth alternative powering options. As the high voltage power supply is external to the device this solution can be acceptable but in big mobility conditions a battery operated Meditech system should be preferred. A detail that should be considered instead is the power consumption of the entire system - also after a further power usage optimisation. The Raspberry PI units tend to consume at least 2mA/h each one or more, depending on the extra boards attached. Another factor if the operating environment: in extremely hot conditions in conjunction with high humidity percentage the batteries are not a reliable solution if used as the main power source of the system.

imageimage

 

LCD display assembly

The LCD display has beed adapted to shown the lowest possible profile and the electronic parts has been reassembled with flexible lightweight acrylic plastic components and super-compact micro foam to reduce as much as possible the weight of the unit. The following image shows the final aspect of the 15 inches display that actually weights about 1 Kg less than original.

image

TODO: A smaller device (e.g. 7 inches) may fit in the Meditech box; this aspect has to be evaluated at the end of the project to give more portability to the entire system without penalising the shown information.

 

The images below shows some details of the assembled display as in the actual experimental version.

 

imageimageimage

 

Assembled views

The following image shows the assembled Meditech box as it appears when is close for transportation and open ready to be used. Not that an extra-12Vplug is provided (to the left of the second image) to power the printer. This device can wok with or without connected power as it has its own internal battery accessed via Bluetooth wireless connection.

 

imageimage

 

Internal view and details

The center of the box, including the HD (1Tb 5 inches, will be replaced by a 2.5 SSD HD, 180 Gb) and the network hub together with the power units. Note that the cables - especially the LAN connections - will be replaced by shorter ones to reduce the wires occupation.

image

 

image

The image above shows the internal of the devices container. It hosts the service PI (with GPS, Accelerometer, Bluetooth for printing and other support features) on the center, the main PI (with database, collector features, WiFi bridge and data organisation and remote feeding, real time clock) to the right side. The left side hosts the Pi dedicated to the audio acquisition and the analog / digital readings through the Bitscope.

Note that to the bottom right side there is a mechanic switch to detect when the box section opening. This information and other related to the health status of the system (i.e. the internal temperature, the fan speed etc.) are controlled by the ChipKit board (right side) sending critical conditions and changes on the system status to the main PI governing the entire architecture. In response to the sensors feeds the main PI can show alarms and warning pop-up windows with high priority, stop some functionalities or shutdown the entire system.

  • in reply to Workshopshed

    I see, Andy. This is a sort of fixed point. Then there is also the solar cells question and some other details that will make the powering in some places a bit tricky. So I kept this problem away until the first great step is finished.

  • in reply to balearicdynamics

    For the Enchanted Cottage I worked out the power requirements partly by reading the data sheets and getting the worst case and partly by measuring with a multimeter. As Lucie mentions, you need to have a supply that can handle the peak rating as well as using the average rating values to work out your capacity.

  • in reply to Former Member

    Hi Lucie,

     

    I am well so and so image ... But it does no matter. Your suggestion is very interesting but as far what I know these cars uses bike or car batteries. And this is exactly what I am doing in some other jobs, e.g. when managing the photography hardware outdoor. Sure this will support the right power and the car / bike battery is not difficult to replace, recharge and so on.

     

    Thinking to one of the environments where this product will be applied, i.e. hot zones of the world, a solution with more "soft" batteries like a couple of laptop batteries in series or similar maybe the wrong possible due to the high humidity and temperature and generally bad weather conditions. With the further disadvantage that these kind of power units will give a very short duration respect the kind of solution you are proposing.

     

    Thanks. Enrico

  • Former Member
    Former Member in reply to balearicdynamics

    good reasoning image  even if you were an expert on power units, you still need to know the final power requirements.

     

    Once you do get to the stage of looking at batteries, some ideas would be those premade for electric wheelchairs, bikes and scooters. Those are designed to provide a relatively high power for a long time and with their intended applications being turning motors under heavy load on and off can provide high "burst" currents.

     

    From the battery to the devices, some premade switchin regulators from ebay maybe?

     

    Hope you are well

     

    Lucie

  • in reply to Workshopshed

    Always good suggestions, Andy ! image

     

    As you know I am not an expert of battery power units image  and this is the reason I plan to calculate the battery at the final stage of the prototype. This idea of the ATX Power supply by battery sounds good; the link you sent is really a bit expensive but it is a good inspiring matter so it has been saved.

     

    When the device is full working it is the time to see the real power needed. For example the 5 inches 1Tb HDD in this moment change the energy balance while I am providing a 120 or 250 Gb SSD. And this is not the only thing.

     

    Don't forget that there is also the solar cells options for powering that needs absolutely a battery at least to gran continuous power. so after the first box has been closed ... I should be time to reopen it.