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System Design: Playing with numbers (Costs)

A project log for PR-Holonet: Disaster Area Emergency Comms

An easy to build, setup, and use emergency communicator for disaster-struck zones with no working power or comms infrastructure.

inventive.prototypesinventive.prototypes 04/29/2018 at 19:260 Comments

Hello! Thanks for taking the time to visit the project! 

This post will explain all costs associated with assembling a PR-Holonet unit, activating it, and operating it. In the ballpark of things, the cost of building a PR-Holonet system as presented in this post will vary from $420 to $600 depending on your final configuration. The differences only affect the capacity of the system to operate in the absence of enough sunlight; as well as the capacity to power/recharge other equipment or the ability to recharge and keep the system operational at the same time. It does not affect the core functionality of sending and receiving messages. It also bears mentioning that I will not be covering shipping costs or taxes. The system has been designed to minimize the difficulty of sourcing the components needed as well as to be used pretty much anywhere; but that also means that I can't, in good faith, give good numbers on shipping costs or taxes to cover all scenarios for anyone to build it.

All cost estimates provided in this post will be in US dollars. Please convert as necessary if you are living in another country. 

This log is long, and it contains a lot of information. I may break it up later in the future. For now, grab a snack, turn some music on, and enjoy.

Thank you!


Assembly Costs

The two key components of this system, the Raspberry Pi 3 B and the Rockblock MK II, should be available at fixed pricing.

The rest of the costs may vary depending on sourcing or capacity. The list of items is as follows:

PR-Holonet is meant to be used in emergency and technology-austere environments. For this reason, the actual list of parts has been put together to enable a system that can:

Following is a list of the actual parts and costs being used to build the system. For a budget version of the system, see the end of the post.

Total Kit Cost: $600

System Core

The core is made up of the Pi, Rockblock, female to female jumper wires, microUSB cables, and microSD card.

Part NameDescriptionCost ($)Source
Raspberry Pi 3 BThe brains of the operation$35.00Adafruit
RockBlock MK IIIridium Short Burst Data
transceiver
$249.50Sparkfun
Samsung EVO microSD cardCapacity
- 64GB
Class 10 UHS 3
Speed
- Write: 60Mbps
- Read: 90Mbps

$19.99Amazon
Female to Female Jumper Wires- 20-pack tape
- 6 inches each
- .1" pitch
$1.95Sparkfun
Anker Micro USB CablesTwo microUSB cables that can be
used to power the Pi or
charge the battery
$9.99Amazon

Project Case

To allow the project to be weather resistant, I've selected a dust-proof, water resistant project box. Down the road I'd like to really test out how hot the system gets and actually test its water-proof worthiness, for now the current case gets the job done.

Part NameDescriptionCost ($)Source
Uxcell Junction Box
DIY Case Enclosure
Gray
Dimensions
- 250mm x 150mm x 100mm
Dustproof
IP65
$21.99Amazon

Power System

The battery and solar charger components are the systems that will vary in cost the most. They are also the components that will dictate whether PR-Holonet can be used to increase the number availability of USB powered tech for relief efforts. The main trade-off in choice selection will boil down to: 

The list of components that will provide the best capability under the current design is: 

Part NameDescriptionCost ($)Source
BatPower PROE 2 ES10
40000mAh
Battery
Dimensions
- 7.2 x 3.2 x 0.7 inches
Capacity
- 40000 mAh
Useful Features
- Can be charged by microUSB cable
or 18V barrel charger
- Integrated LED "Flashlight"
- Can charge itself and power/recharge
systems simultaneously
- Can be used to power a laptop
- Can output up to 90W of power
$169.99Amazon
ALLPOWERS 36W
Foldable Solar
Charger
Dimensions
- 12.8 x 7.7 x 3.1 inches
Weight
- 3.02 pounds
Useful Features
- Higher number of PV cells
than ~20W systems means
more comparative power for
the same amount of sun
- Two 5V/2.4A ports ( up to 12W
output per port)
- One 18V/1.5A port ( up to 27W )
- If your battery supports 18V
power input, then it can charge
faster than using regular USB 2.0
to charge it
- Water-resistant (according
to marketing material)
$89.99Amazon

Activation Costs

Activation costs are comprised of 3 parts:

None of these services require a contract, so the system can be used for the time needed and then deactivated. 

Rock7 Core 

To use the Rockblock MK II, a monthly activation fee of an estimated $14 is required. There is no minimum yearly commitment required. Use as needed.

Amazon AWS (Lambda Services) 

Amazon's pricing model is based on resource consumption. PR-Holonet easily falls in their free of cost range. However, you will need to create an account and enter your credit card information. No contract required. 

Twilio

Twilio charges a monthly fee for providing phone numbers. The fee can vary, in my case it is $3 per month for 1 number. Data is billed per message. No contract is required.


Operating Costs

Operational costs, for the effect of this post, will refer to any costs other than monthly activation fees. For PR-Holonet, this is encompassed by the data transmission and handling costs. PR-Holonet is a low-bandwidth communications system; the data transmission costs are due in its majority to the satellite gateway services. 

The operational costs are also encompassed by the same three services mentioned in the previous section: 

Rock7 Core

Rock7 charges for every message sent and received over its satcom gateway. Some RockBlock actions, such as pinging the servers for pending messages, may incur in costs. All costs are based on a unit of cost called a "credit". A credit is any burst of data sent or received from a RockBlock MK II that is 50 bytes or less. All transmitted and received data is charged based on the "credit" scheme. 

The cost of each credit is based on the total amount of credits acquired at the time of purchase. Credits do not expire and can be used so long as there is an active account and Iridium transceiver available. Credits are also shared among all Iridium devices registered to it. 

At present the prices for credits are (amount of dollars subject to change based on currency exchange values): 

Number of Credits Cost per Credit British Pounds (£) / US Dollars Bundle Price British Pounds / US Dollars ($)
100 Credits£0.11 / $0.15£11.00 / $15.16
200 Credits£0.10 / $0.14£20.00 / $27.56
500 Credits£0.09 / $0.12£45.00 / $62.01
1000 Credits£0.08 / $0.11£80.00 / $110.24
2000 Credits£0.07 / $0.10£140.00 / $192.92
5000 Credits£0.06 / $0.15£300.00 / $413.40
10000 Credits£0.05 / $0.08£500.00 / $689.00
20000 Credits£0.04 / $0.06£800.00 / $1102.40

Amazon AWS (Lambda Services)

Amazon AWS is NOT FREE. However, due to the low use of computational resources required by PR-Holonet it falls within the no-charge tier for Lambda services. Thus, there is no additional impact to operating costs because of cloud processing. 

Twilio

Twilio charges $0.0075 per message for the first 5 million messages routed through their services in the US.


An alternative, budget version of PR-Holonet

If cost is a priority, here is a version of PR-Holonet that will get you a working system for close to $200 less in parts. Be mindful that you compromise:

Total Kit Cost: $418.85

System Core

Part NameDescriptionCost ($)Source
Raspberry Pi 3 BThe brains of the operation$35.99Adafruit
RockBlock MK IIIridium Short Burst Data  transceiver$249.50Sparkfun
Samsung EVO microSD cardCapacity
- 32GB
Class 10 UHS 3
Speed
- Write: 60Mbps
- Read: 90Mbps
$12.99Amazon
Female to Female Jumper Wires- 20-pack tape
- 6 inches each
- .1" pitch
$1.95Sparkfun
Anker Micro USB Cables2  microUSB cables that
can be used to power the
Pi or  charge the battery
$9.99Amazon

Project Case

Part NameDescriptionCost ($)Source
Uxcell Junction Box
DIY Case Enclosure
Gray
Dimensions
- 250mm x 150mm x 100mm
Dustproof
IP65
$21.99Amazon

Power System

Part NameDescriptionCost ($)Source
Anker
13mAh
Battery
Dimensions
- 7.2 x 3.2 x 0.7 inches
Capacity
- 13000 mAh
$31.99Amazon
Allpowers
21 W
Foldable Solar
Charger
Dimensions
- 12.8 x 7.7 x 3.1 inches
Weight
- 3.02 pounds
Useful Features
- Integrated 6000mAh battery
$54.99Amazon

References, Links, and Resources

  1. Amazon.comhttps://www.amazon.com/ ]
  2. Sparkfun.com [ https://www.sparkfun.com/ ]
  3. Adafruit.com [ https://www.adafruit.com/ ]
  4. Amazon Lambda Pricing [ https://aws.amazon.com/lambda/pricing/ ]
  5. Amazon S3 Pricing [ https://aws.amazon.com/s3/pricing/ ]
  6. Rock7 Core Pricing [http://www.rock7mobile.com/products-rockblock ]
  7. Twilio Pricing [ https://www.twilio.com/sms/pricing/us ]


You Made It!!

That is the end for this log. I hope it has provided a clear understanding of the costs associated with building and operating PR-Holonet. If you have questions, send them my way!

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