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LoFi

LoFi is a very low cost ($5), small, auto-transmitting module. Preassembled and preprogrammed. Simply attach to your appliances or projects!

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This project was created on 06/20/2014 and last updated 2 hours ago.

Description
Like many hackers and hobbyists, we dream of a smart home. Although there are third-party transceiver modules and data loggers on the market, they are too expensive and complicated to deploy in volume.

LoFi is a very low cost ($5), small, auto-transmitting module. All you need to do is to attach the modules to interesting appliance circuit points or sensors throughout your home and garden. The data arrives on your PC or can be sent to the Internet with a WiFi hotspot.

No programming, no protocols to learn, and no carrier boards for you to make. Just attach!

Using your desktop or laptop, you can set trigger levels on individual modules to tell them when to transmit. For example, send an update when the voltage changes by more than 1 V on the vibration sensor near the garage door opener. You can also set the module on a timer, such as hourly on your garden monitor.

The possibilities are endless!
Details

SENDER

The sender module is compact (1.25 inches squared) and operates from 1.8 to 5.5 V at an average of only 20 microamps. The module consists primarily of an Atmel ATtiny84A which monitors the inputs and outputs the data. A red and green LED provides visual status. In volume, the sender module should cost less than $2 in parts.

The sender module has:

(5) analog or digital inputs with configurable trigger thresholds

(1) digital trigger

(1) internal temperature sensor

(1) voltage reference (useful to convert numbers into voltages)

(1) optional CR2032 coin cell holder

(1) optional pushbutton

CONFIGURATION

Without any programming knowledge, the sender module can be configured to transmit:

  • (a) On power up
  • (b) When any analog input goes above a certain value
  • (c) When any analog input goes below a certain value
  • (d) When any analog input changes by more than a certain amount
  • (e) Periodically from 10 seconds (per FCC) to 18 hours

Configuration is accomplished using a laptop or desktop connected via a standard FTDI serial cable (Adafruit #70).

TRANSMITTER

The actual transmitter on the sender module is an off-the-shelf, inexpensive 433 MHz AM board and a simple wire antenna. The transmitter can be removed to connect a serial cable for configuration and direct reading. Therefore, this could be used as a wired device.

IS 433 MHz VIABLE?

I purchased the raw transmitter/receiver boards in new condition for $1 on eBay. There are tons of vendors selling them. I was skeptical that such an inexpensive part would produce acceptable results.

Surprisingly, even with a simple wire antenna and only 3 V, the transmitter/receiver pair was successful indoors through walls at more than 75 feet.

Reliability is accomplished with the software algorithm in the LoFi microcontroller:

  • Normally quiet (no transmission) to cooperate with other senders
  • Preamble burst to wake the receiver and set the gain
  • Oversampling on the receiver to ignore minor noise
  • Require stop bit to ignore radio static when not transmitting
  • Error-correcting checksum to correct moderate noise and detect major noise
  • Configurable fine-tuning of bit rate to compensate for inexpensive internal oscillator
  • Message id to detect missing packets
  • Configurable post-trigger messages to increase the odds of a timely packet for weaker or more distant transmitters

In any event, because the transmitter and receiver are detachable, and because they communicate using conventional serial data, you can use different transmitter/receiver boards and spectrum if you prefer. Put another way, the LoFi modules are not dependent on the type of transmitters.

OPEN AND EXPANDABLE

LoFi is designed to open up the devices in your house. Keeping with that philosophy, LoFi is designed to be open itself. This will allow others to apply their creativity in delivering compatible variations. The completed project will be under Apache License, Version 2.0, so that you can use any or all, for fun or commercially.

I’m looking forward to seeing the shields that are produced -- prepopulated with specific sensors or connectors. Some companies will target specific appliances (doorbells, sump pumps, garage door openers, garden monitors, model rockets) while others will create different form factors and features (long range transmissions) for the LoFI sender itself.

Most users will employ the module as-is, however it is definitely hackable. With the transmitter detached, an ISP6 cable can be connected to reprogram the ATtiny microcontroller with whatever modifications you want to the open source code. It is written in C using the free AVR Studio 6.2 with avr-gcc. 

See the System Design Document for complete license details and tools. There are no third-party licenses or restrictions.

NEXT STEPS

The working prototypes successfully proved the concept. The listener/receiver PCB has now been manufactured and needs testing. I’ll continue to post results of experiments and other milestones as they occur.

The final goal will be to publish a tested baseline end-to-end solution...

Read more »

Components
  • 1 × C1 Capacitor 10µF (CC1206ZKY5V7BB106)
  • 1 × IC1 Microcontroller, SOIC, ATtiny84A (ATTINY84A-SSU)
  • 1 × J1 Connector, 6-pin right-angle female socket (801-87-006-20-001101)
  • 1 × LED1 Status LED, 1210, bicolor (LTST-C155KGJRKT)
  • 2 × R1, R2 Current-limiting resistor, 220Ω (RC1206FR-07220RL)
  • 1 × R3 Pull-down resistor, 100kΩ (RC1206FR-7100KL)
  • 1 × J3 (optional) ISP6 programming header (75869-131LF)
  • 1 × Configuration cable FTDI USB-to-serial TTL 3.3V (TTL-232R-3V3 Adafruit #70 http://www.adafruit.com/products/70)
  • 1 × Schottky diode SOD123 MBR0520L 20V

Project logs
  • Good Things Come in Small Packages

    2 hours ago • 0 comments

    I’m experimenting with some novel enclosures for various installations of LoFi around the house and yard. I need to make an impact for the stage 3 judging.

    I ordered some more m&m’s candy tins, because they are an excellent size and have a clear top window. When you buy them, you can customize the candy pieces with logos and writing. So, I used the Hackaday Prize logo.

    LOFI in an IPHONE CHARGER

    I appreciate the industrial design talent at Apple. Here is LoFi inside of a standard Apple power adapter, which is approximately 1 inch cubed (25 mm). In the USB slot, a small panel holds a light sensor, an ice cube LED, and the antenna. Yes, it really works.

    The main board holds the CR2032 coin cell and has a standard 0.1 inch header for the transmitter and accessories. There is enough room leftover in the center for additional sensors.

    LoFi runs for over a year on a single coin cell. Although I usually use a plastic holder, metal holders are cheaper and use less space. I designed a LoFi board with pads on the back for the ground terminal of the cell, and then bent the metal holder tabs around to the front of the board to attach the positive terminal.

    Unfortunately, I made a mistake. Upon inserting the coin cell, nothing happened! I checked my connections, looked for shorts, and even wrongly suspected the new ultra low dropout diode.

    The problem turned out to be my failure to account for the height of the solder mask. You see, the solder mask goes on top of the copper layer, and thus is slightly higher. The back of the coin cell was resting on the solder mask and not making contact with the pads on the back of the board. Applying a thin layer of solder to the pads raised it up enough to make contact.

    I have a really interesting application (which I’ll keep secret until it is ready) where LoFi needs to fit inside of a 1-inch circular tube, rather than 1-inch square. The tube was machined from a green medical grade Delrin/acetal block.

    As you can see, LoFi managed to squeeze inside. A blue lens is machined to fit on top.

    To make LoFi fit in the smaller space, I needed to insert a longer header in the front of the transmitter and bend it back 180 degrees (see red arrow below). Doing so allows the socket to overlap the bottom of the board and close the gap (blue arrow). There is enough room in the tube to fit a helical antenna – with the accompanying reduction in range, of course.

    If you liked this write up, consider giving LoFi a skull if you haven't already. Thank you!

  • Outdoor Temperature Monitor

    a month ago • 1 comment

    In the previous logs, I’ve shown LoFi in the remote corner of the basement and in the garage. Now, LoFi ventures outside to the garden to measure temperature and light levels.

    A ‘My M&M’ silver favor candy tin (intended for weddings or parties) is the perfect size container for LoFi, the AM transmitter, a solar panel, coin cell (underneath the PCB), and various sensors. A clear lid permits light but blocks bugs, dirt, and hopefully rain. The transmitter antenna wire sneaks out the side through a #54 drill hole.

    A foam liner was added to the candy tin to avoid electrical shorts. Even though the container has a non-conductive coating to avoid contaminating the candy, I've been burned by scratched or worn areas in the past.

    When there is adequate sunlight, the Adafruit Round Solar Panel Skill Badge (#700) powers the device. This solar panel was chosen because it fits so well, and provides the maximum voltage with good current. At full sunlight, the panel likely exceeds the ATtiny 5.5 V operating limit, but will stay under the absolute maximum of 6 V and has 0.2 volts or more dropped by a Schottky reverse-protection diode.

    Aside: There is a thin clear plastic film covering the Adafruit badge to protect it from scratches. The film had not yet been peeled off in the above picture. The badge is quite lovely when the film is removed.

    The ATtiny internal temperature sensor and voltage reference are ‘no-cost’ inputs. An added photocell provides brightness data, and was selected to be sensitive to conditions after the solar panel yielded to the backup battery.

    With wireless, it is nice to get immediate readings rather than logging to a flash as I have had to do in past experiments: http://www.robotroom.com/Weather-Station.html

    This was not my first choice of locations for LoFi, but I discovered that a spot of land was already claimed by a toad in a hole.

  • Garage Door Monitor

    2 months ago • 1 comment

    An example usage of LoFi is to monitor when the garage door opens and closes, as well as when the garage’s interior light has been left on.

    LoFi is designed to perform such tasks with minimal added parts and no programming. However, Ralph Doncaster (Nerd Ralph) http://nerdralph.blogspot.com/ commented that LoFi should be able to run on a coin cell. So, this is a good opportunity to experiment with that as well.

    Ralph pointed me to a study demonstrating that a bulk capacitor extends the life of a coin cell by supply current during peak demand of low-duty-cycle devices. I also added a Schottky diode to prevent the battery from being charged when the LoFi board is attached to a computer. I almost learned that lesson the hard way when a nasty smell spewed from one of my NiMh battery packs. An improved board has already been designed to include the coin coil and diode, as well as a capacitor connector.

    A simple cadmium sulfide photoresistor cell detects the brightness of the garage, not only to determine if someone has left the light on, but also as a potential non-mechanical means of detecting a change in the door state. Primarily, the garage door position is detected by an Adafruit tilt ball switch (#173).

    Given that LoFi should cost less than $5, it only makes sense to use an equally expensive case. LoFi fits well in a Tic Tac box. The container is mounted to the garage door with Velcro hook and loop fasteners.

    I quickly discovered a problem with my steel garage door: it blocked the transmitter signal (L shaped house). The challenge was overcome by repositioning LoFi to the top of the garage door, such that the antenna stuck out above the top panel.

    All in all, this experiment is a success. LoFi correctly detects a change in garage door state, as well as delivers periodic updates on the door position, light level, temperature, and battery voltage.

View all 9 project logs

Build instructions
  • 1

    LoFi is expected to be delivered ready-to-use (prepopulated and preprogrammed). These instructions are for people that want to build LoFi themselves from scratch or are interested for curiosity. These instructions are expected to change as the project nears completion.

    Download and decompress the PCB layout and source code [future] files from this project page.

  • 2
  • 3

    Open the PCB layout folder and locate desired PCB you'd like to have made. For example, LoFi-PCB-Layouts/Sender/LoFi-Sender-v5.zip. Drag that zip file onto the OSH Park web page to upload it.

See all instructions

Discussions

wifiwaves wrote 7 days ago null point

Congratulations for making the cut to the next level, David.

Onward and upward...!

Are you sure? [yes] / [no]

David Cook wrote 6 days ago null point

Thank you!

I spent most of Monday clicking the refresh button. I was overjoyed when the list appeared with LoFi on it. Then, almost immediately, I realized I would need to step up my game to compete with some of the other semifinalists. It will be an exciting, busy, and swift month.

Are you sure? [yes] / [no]

Rjpope42 wrote 13 days ago null point

Great project and great idea, I must admit I'm jealous it wasn't mine :)

I would be building some right now, but I'm not clear on something, it looks like the reciever boards are made, but you haven't worked out the reciever code?

Unfortunatley I don't have any other 433MHz recievers laying around to do the job

Again, great project and good luck!
It's nice to see something this useful and practical!

Are you sure? [yes] / [no]

David Cook wrote 13 days ago null point

Thank you for the compliments on the project! The receiver firmware is currently able to receive the message, decode the hamming, and pass the message to the PC. The PC is able to indicate the message arrived and log it to a file. However, the receiver and PC need to programmed to perform that task through Wi-Fi. Also, the PC software needs to be able to show all of the senders on a site map and let you view the messages on the screen. So, there is definitely work to complete -- but I believe there is enough time to do so.

I appreciate your kind words and support!

Are you sure? [yes] / [no]

Jasmine wrote 18 days ago null point

Hello David, I've just checked your project and it meets the requirements, so it will be considered for the next round of The Hackaday Prize. Thanks & good luck.

Are you sure? [yes] / [no]

David Cook wrote 14 days ago null point

That's wonderful news! I see you and the team seem to be double-checking all 400+ projects. Based on their replies, some builders are grateful, some seem to have abandoned their projects, and a few seem to be giving you attitude. Therefore, in case anyone else doesn't say it: Thank you, Jasmine. You're efforts to help everyone across the starting line is truly decent.

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TacticalNinja wrote a month ago null point

Hi David,

I've been fascinated by, and learned so much from your work since robotroom.com (I've been reading it since I was 16! I remember sending you an email regarding an H-Bridge design back then.)

I got a question though, I'm not sure if I missed something from your write up, is it possible to have a few of those transmitters transmitting at the same time with one receiver node? If so, how did you manage to receive the signal simultaneously? TIA, I'll keep posted.

Are you sure? [yes] / [no]

David Cook wrote a month ago null point

Hello TacticalNinja -- I have had a lot of fun writing up articles over the years. I'm glad you've enjoyed reading them!

Yes, LoFi supports multiple transmitters for a single receiver. But, as you suspect, it is not possible for a single receiver to receive messages from more than one transmitter on the same frequency at literally the same time. Instead, the system relies on two important conditions:

1. The transmitters are low duty cycle, meaning they spend most of the time being quiet (which also extends battery life).

2. The transmitters repeat data (retries) at slightly uneven intervals to avoid overlap of all of the messages.

I've found this works really well. For more congested conditions, you can use multiple receivers at different frequencies.

Are you sure? [yes] / [no]

TacticalNinja wrote a month ago null point


Hi David,

Thanks for the quick reply. I was also thinking of the same mechanism since I could not find any other way to sort out multiple transmitter nodes using a single receiver node without some sort of ACK signal.

Keep those projects coming! :-)

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Eric Tsai wrote a month ago null point

David, we have pretty similar projects. Your MCu design is a lot more battery efficient than mine. I've been using several AA batteries to keep mine running. I'll have to investigate your ATtiny design to see if I could incorporate it into my Arduino sensor node design.

Thanks for the inspiration! I linked your project in my hackaday.

Are you sure? [yes] / [no]

David Cook wrote a month ago null point

Hi Eric -- Thank you. You sure have a wide variety of monitoring ideas on your project page!

I'm using the deep sleep mode with a watchdog interrupt to wake up, if that helps you any. The sensors are powered down until they are read, and my board doesn't use a voltage regulator. So, that definitely keeps current usage to a minimum.

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Minimum Effective Dose wrote a month ago null point

I love the concept behind this project, it's fantastic. I'm very excited to see how it develops. Really sharp work.

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David Cook wrote a month ago null point

Thank you so much! The listener + receiver + WiFi board (effectively becoming a LoFi hotspot) has just been finished. After the boards arrive I'll post pictures.

Are you sure? [yes] / [no]

radicalbiscuit wrote a month ago null point

I'm excited at the prospects this offers. I've preemptively purchased a few receiver-transmitter pairs and I anxiously await availability.

Two questions, and I must apologize for the first:

When might these be mass produced and available to an end user like me?

What am I supposed to do with all these extra receivers? :P Maybe I can set up multiple receivers for a wider range.

Thanks for your work! I'm most excited about two projects in the world right now: ISEE-3 and this.

Are you sure? [yes] / [no]

David Cook wrote a month ago null point

Hello radicalbiscuit,

Thank you so much for the kind words. It is very motivating when someone posts a positive comment like yours!

1. I've been approached by a wonderful reseller about producing the product. But, I need to finish it first. I'm working on the listener board now (up to this point, I've been using a sender board in reverse.) I can't tell whether it would be viewed positively or negatively by the judges for a product to be 'in stores' before the conclusion of the contest.

2. Ha! I also have a bunch of extra receivers. Whenever I dig in my parts container for a transmitter module, I have to toss a couple of receivers back. Nope. Nope. Yes! Maybe you should start a project called 'Triangulation Using Spare AM Receivers'.

David

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radicalbiscuit wrote a month ago null point

While this wouldn't solve the problem of extra receivers, it would utilize transmitters and receivers in pairs: have you considered meshing, standalone Lofi repeaters? The purpose being, of course, to extend range of the system indefinitely.

Similar to APRS, when an error-free message is heard by a receiver/repeater and has not yet been received before, it will transmit the same message, perhaps altered to indicate the number of hops the message has taken. Other repeaters will also transmit the message and in the end, the master receiver picks it up.

This could be well-suited to a wall wart form factor, although wireless functionality may also work well if your receiver commands power efficiency in the same neighborhood as your transmitter.

And there's no reason these couldn't double as the triangulation devices mentioned in your reply to my original comment. Given known locations of the repeaters, a plot of all the Lofi senders on OpenStreetMap is only a calculation away... :D



Once again, thanks for your work. Looking forward to seeing and reading about the new boards!

Are you sure? [yes] / [no]

David Cook wrote a month ago null point

Range hasn't been an issue so far, however you are definitely on to something regarding making a basic mesh network. If you consider a far away or terrain-constrained transmitter at only 3V, a repeating receiver with a 12 V transmitter and nicer antenna could significantly broaden the total network range without adding much cost. Good idea!

Are you sure? [yes] / [no]

Pixel Pirate wrote 2 months ago null point

Sorry if I'm being OCD, but those traces on your PCB make me cringe...

Are you sure? [yes] / [no]

David Cook wrote 2 months ago null point

Someone once said, "It should be 'CDO', because then it would be in alphabetical order". But seriously, I'm always open to suggestions. What would you do differently? The Copper Connection file is listed in the downloads. Could you make some sample edits and send the file to me?

Are you sure? [yes] / [no]

Pixel Pirate wrote a month ago null point

Mostly it's just aesthetics cringe. I can't stand routing a trace that isn't a 45 degree angle. Nor can I stand uneven spacing.
IT's just a psychological thing.

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Ron wrote 2 months ago null point

Nice project Mike, wireless and ATtiny is the way to go

Are you sure? [yes] / [no]

David Cook wrote 2 months ago null point

Thanks Ron. Yes, the ATtiny has so many built-in features that this project needs: oscillator, deep sleep, long-period watchdog wakeup, voltage reference, temperature sensor, EEPROM for settings, and so on.

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wifiwaves wrote 2 months ago null point

David,

Just something for everyone to be aware of...

The FCC has specific requirements for using transmitters. The FCC has made provisions for unlicensed transmitters throughout the radio spectrum. You can operate just about anywhere, but there are restrictions on the field strength, type of emission, and duty cycle that the system designer needs to be aware of before planning and deploying a system.

Unlicensed transmitters are covered under Part 15. The specific section covering these particular transmitters is at:

http://tiny.cc/a519hx

Briefly, the transmitters under discussion in your project are limited by two provisions:

15.231 (a)

The transmit on time is limited to a maximum of 5 seconds. Video, voice, and control of toys is prohibited, and the transmitter must be manually triggered. No periodic operation is allowed, except to verify system operation. In this case, the transmit time is limited to 2 seconds per hour (1/1800 duty cycle).

15.231 (e)

The on-time is limited to a maximum of 1 second. The off-time shall also be at least 30 times the on time, with no less than 10 seconds between transmissions. The key to using this section is to have the system transmit in short bursts, with a 10 second off time. No restriction on application or modes, but you have to pay attention to the duty cycle.

I ran into these issues when I was designing a remotely located turbidity sensor protecting a surface drinking water supply. Our design accommodated these requirements with no particular impact on the device functionality. We are using this long range device:

http://tiny.cc/lg39hx

It should be noted that where the device performs a fire, security, or other life safety function, the device may transmit for the entire duration of the alarm condition. While not prohibited, one should give due consideration to using homebrew devices in such situations. Commercial devices are rigorously tested under numerous circumstances to insure that they will operate properly when necessary.

Good RF design practice guidelines (aside from the FCC requirements) 'require' that a transmitter not use more power than is necessary to accomplish the given communication. This keeps the spectrum cleaner, and allows greater density. It also keeps the power supply requirements lower.

While these transmitters may not be seen at any great distance, following these limitations keeps one from having 'interesting' discussions with the FCC.

Onward and upward...!

wifiwaves

Are you sure? [yes] / [no]

David Cook wrote 2 months ago null point

This is great information. You clearly have the voice of experience. : )

At present the duration of messages is 200 ms. I'll make the default configuration include a quiet period of 10 seconds.

Fortunately, LoFi is not tied to a specific transmitter, frequency, or antenna. So, it will be possible to select appropriate modules for a region, governing body, or interference profile.

Are you sure? [yes] / [no]

wifiwaves wrote 2 months ago null point

David...great work!

For those interested in these kinds of transmitters/receivers, here are a ton of devices out there. Search for "key fob remote control" and a plethora of transmitters & receivers will show up. There are a couple of other bands available, most notably 418MHz (with little interference).

I find this device to be extremely helpful when working with these kinds of devices:

http://www.iautomate.com/products/rf-explorer-433-mhz-spectrum-analyzer.html

No pecuniary interest...just a fine device for cheap.

Keep up the great work!

wifiwaves

Are you sure? [yes] / [no]

David Cook wrote 2 months ago null point

Hi wifiwaves,

Hmmm. 418 MHz sounds very appealing. Thus far, I haven't had problems with interference in my home, but surely other people will. This would give people a choice. Also, perhaps I could build listener that could connect to two receivers, thus permitting more devices.

Thanks for the tip!

David

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Dave Jakopac wrote 2 months ago null point

David, the Sandwich robot I built--based on your book--still runs in demos at Chibots events. Great project and I'm looking forward to seeing the results.

Are you sure? [yes] / [no]

David Cook wrote 2 months ago null point

Hi Dave!

On a recent family vacation, we played a game where we were asked about our most prized personal position. I said 'Sandwich' and my family looked at me like I was crazy. Sure, there's epoxy coming out the coupler, ratty wires, and a few cuts that went slightly too far, but it still works and I built it myself. So, I am sincerely pleased to hear your robot is still running as well.

David

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barcellos.alvaro wrote 2 months ago null point

Slow and secure and constant as into the Voyager. My vote sure.
Could open a trend in remote control and sensors.

Are you sure? [yes] / [no]

David Cook wrote 2 months ago null point

According to Wikipedia, Voyager has a bit rate of 40 bits/s without error correction. So, I'm pleased to have 1970's technology beat. Oh, wait, it can transmit up to 115.2 kbit/s? Never mind.

Thanks for the vote!

David

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Mike Gordon wrote 2 months ago null point

This looks great! I can think of multiple uses around the house for a few of these. With that said, how about adding a 1-byte transmitter identifier character to the header to allow for independent sender/transmitters to be used in the same environment? The identifier could be set in the same interface as the trigger parameters.

It doesn't show in the project, but are you also planning a corresponding output module to plug into the 433 receiver? I'm thinking a small board that would read the transmission and duplicate the states out to corresponding analog and digital pins, either momentary, or latching until a new transmission is received that would change a pin's value, or even for a user configurable (on the output board) number of milliseconds

What is the power consumption of the input board and transmitter combination at rest and while transmitting? One application I'm thinking of would be to send an alert when one of 3 doors opens and closes, possibly with a status update on one every 10 mins. I'd like to power it off of a couple AA batteries, but not if I'd have to change them every couple weeks. Any ballpark estimate on that?

Are you sure? [yes] / [no]

David Cook wrote 2 months ago null point

Hi Mike,

Currently the header is six bytes and contains:
'L', message length, sender address, message id + retry id, command, subcommand

Therefore, yes!, you can have many transmitters. Also, note the message length byte and command bytes will permit the receiver to be able to deliver a variety of messages that it doesn't know anything about (forward compatibility).

As for the receiver, I am presently using a LoFi sender configured 'backwards'. But, I plan to make a special board to permit direct uplink to WiFi.

As for power consumption, I just added a log post inspired by your question. The answer is: a couple of AAs would power the device for a decade.

David

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João Lucas Torres wrote 2 months ago null point

Great work! I really love low cost networks. I'm finishing my final course project and it's about infrared networks.

Waiting news of this project.

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David Cook wrote 2 months ago null point

Thank you for the encouragement. New boards arrived today, so I'll have interesting material to post this weekend.

Are you sure? [yes] / [no]

Hjorgenogueira wrote 2 months ago null point

what a great project David, i always thought simple RF without complicate and expensive protocols like zigbee and other would do the trick most of the times...i think i will try to make one of these just to try out, unless if you have already spares ones and are planing to sell these...?!
thanks for the inspiration and sharing with us!

Are you sure? [yes] / [no]

David Cook wrote 2 months ago null point

Thank you! When the project nears production quality, I'll remember to upload an object file as well, so that you can program bare chips without having to reproduce the compiler environment. That being said, I am optimistic that the ready-to-run modules will be manufactured and available from our favorite sellers.

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Neal McBurnett wrote 4 days ago null point

The cool thing about 802.15.4 and stuff like zigbee that builds on it is that besides being a standard, and super-low-power, it can also fit in to a standard homenet, and be addressable securely and globaly via ipv6 (6lowpan). Can you contrast your solution with a cheap, bare-bones 802.15.4 solution in terms of cost, etc?

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David Cook wrote 4 days ago null point

The XBee module is wonderful and much more powerful.

However, LoFi is:
* Lower cost (about $2 in parts + $1 for the transmitter)
* Lower power (10 mA transmit, 13 uA idle)
* Smaller size

Both have their place. If you simply need something to monitor some analog values (sensors) and run a long time on a coin cell, then LoFi is a good choice. If you need a communication channel, then XBee is a good choice.

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DeepSOIC wrote 2 months ago null point

I want this one to go straight into our science lab!

Are you sure? [yes] / [no]

David Cook wrote 2 months ago null point

All right!

Your thumbnail freaked me out until I clicked on it.

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Mike Szczys wrote 2 months ago null point

Hi David! This already looks like a fantastic entry for The Hackaday Prize.

I actually stopped by to mention that I'm a huge fan of yours. Your book "Robot Building for Beginners" was the second book I read when beginning to learn about electronics and in my mind the most formative. Thanks so much for sharing your knowledge and passion!

Good luck with this entry.

Are you sure? [yes] / [no]

David Cook wrote 2 months ago null point

Wow! Thanks Mike. That means a lot to me. I visit Hack A Day daily to learn from others and to be inspired. Your site does so much to encourage science that I absolutely had to contribute an entry to your contest. By the way, I am really impressed with how easy it is to post and edit projects here.

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