Re: [DIYbio] Amazon unintentionally solves "low cost lab automation device" challenges

My answer applies to various lab devices, not looking to make this only about OpenPCR.  The arduino board or other microcontroller board can very likely be designed out, if using the Fire tablet.  You only need an op amp circuit to convert the analog inputs to "something the tablet can read" (suggestions below).  In cases where this isn't the best design, then only a simple external A/D chip is needed.  No other processor such as arduino is needed, and especially no extra firmware.  Having zero firmware eliminates a big chunk of the design effort which also translates into hidden cost.  Lab devices are low volume, so the development costs are a big factor.  I am still against using Arduino in designs due to their "high cost, low performance" results.  Other solutions are better as I've mentioned before, and progressively appear.  The $5 Raspberry Pi Zero just announced is powerful and a good fit, but still, an external controller can be eliminated with good design, by allowing the tablet hardware and tablet software to do the work.  The only external hardware should be the minimal analog hardware, such as the analog buffers and sensors and transducers themselves.

I agree, no one buys an extra laptop specifically for communication to lab automation devices, but having that as part of the overall design is clunky, complex, and if USB is needed, then there is a limited-length physical wire involved.  "Here's my great low cost device, now just bring along your $1000 laptop or $600 smart phone to use it!" - No thanks, and that is often not practical in field use anyway.  Which is why many published-then-hyped-by-Wired-magazine devices fail to really deliver.  Total system cost and complexity must be considered, as well as ease of use.  Simplicity is often the better design.

When I say above "something the tablet can read", there are analog inputs & outputs on the Fire that are available to interface to external circuits.  They just aren't as easy.  If the Fire is someday ready-made with *three simple metal contacts* on the outside of the case, for I2C communication, it would be a cakewalk.  That's why Jeff Bezos needs some email sent to him :-D   For example, the headphone/mic jack of the iPhone has been used to plug in several popular analog measurement devices.  The Square credit card reader for example, or the little spinners to measure wind speed.  On the low end Fire, these are available too.  Although not as convenient, the overall cost is lower and the design is simpler.  Even the recent thread about conductivity measurement could be done on the $35 Fire without any external controller needed, and thus also no firmware needed, by using some simple analog chips in a nice design.  It's likely that the OpenPCR or any temperature controller could use a temperature sensor directly wired to a voltage controlled oscillator which connects directly to the microphone input, for example (LM35 to an LM555).    The OpenPCR already uses the LM35 or a similar sensor.  The LM555 designed with bias components costs only an additional $0.30, max.  If multiple temperature sensors are required then the analog design could mix those in too, the tablet would easily discriminate the inputs of each sensor.

I don't have OpenPCR's Bill of Materials and I don't know if it was ever published (it should have been, in order to be named Open).  Assuming the costs involved, $5-$10 LCD display, $25 arduino w/ USB, $1 USB cable, $2-$3 added enclosure cost due to cut outs for the LCD and arduino mounting hardware, the current BOM definitely loses.  Plus firmware development costs and firmware support costs (time & effort).  It should be noted that OpenPCR is "Not arduino, it is atmega firmware" (OpenPCR does not use arduino software because arduino software was not sufficiently powerful).   Additionally the features added with the tablet (wifi, bluetooth, touch screen, near HD display, memory card slot, internet/cloud support, web browser), make the Fire possibly a huge winner.  Likely the Fire should be looked at to serve as the basis for other lab devices such as, cell counting, gel photography (note; the 720p camera is not comparable to current high end smartphones, but is probably comparable to 2nd generation iPhones), pH meters, colorimetric / fluorescence meters, PCR or incubator temperature controllers, lab robotics controllers, pump controllers, and so on.  The added feature of having the hi def screen even when purposed as a simple control device allows for graphical plotting directly to the user, of historical data or real time data.  What are the device's limitations?  Are the Amazon adverts a limiting factor to usability?  Is the Bluetooth capability limited by the hardware?  Is the camera sufficient for imaging use?  Is Amazon's pricing structure going to limit the longevity of the low end Fire line, thus diminishing the Fire's value as a common platform?  It should be noted that the low end Fire has been rooted to run android, so presumably low level software development is possible.  Amazon has resumed normal pricing of the low end Fire so it's back to $50, though I assume it will ultimately return to the $35 price.


Note- If anyone does use the Fire or another inexpensive tablet or smartphone as the basis for a lab device platform, then make sure to physically disable any unused hardware for when the device inevitably gets hacked from outside.   I wouldn't want a device in the lab which has a hacker, or a government, monitoring the microphone, or snapping unauthorized photos from the built-in camera.  Simple black electric tape over each camera solves the photo hacking problems, and wire cutters for the microphone and speaker.  Don't trust any internet-connected device to be safe even if it is set to airplane mode.

## Jonathan Cline  ## jcline@ieee.org  ## Mobile: +1-805-617-0223  ########################    

On 12/3/15 10:50 AM, Bryan Jones wrote: