Knocking a microcontroller into sleep mode and waking it up on demand or in intervals is common practice in many low power applications, enabling devices to stay in operation for years on a single coin cell battery. Since there are tons of applications where you might want to do similar things with a Raspberry Pi, [Patrick Van Oosterwijck] created the LiFePO4wered/Pi. The module that snaps on to eight GPIO pins of a Pi, extending it by a long life LiFePO4 battery, a charging regulator, and a proper power management. Obviously, it also makes a great UPS.
[Patrick] realized this project by expanding his already available and equally useful LiFePO4wered/USB charging regulator module by a low power MSP430G2131 microcontroller and a load switch. A daemon on the Raspberry Pi speaks to the module over I2C, allowing you to schedule a wake-up timer, let your Pi autoboot after a power outage or just read out the current battery voltage through a command line tool. Once the Pi is safely shut down, the microcontroller will also go to sleep, resulting in a standby current of 8 uA for the whole system. Together with the 500 mAh LiFePo4 cell, that’s theoretically low enough to send your Pi-ncess into a seven-year-long sleep.
LiFePO4wered/Pi is not only good for sleeping, though. [Patrick’s] runtime tests show, that the 500 mAh cell will power a Raspberry Pi Zero and a WiFi dongle for about two hours. Because the Raspberry Pi and many USB peripherals won’t complain when only 3.2 V are present on the VBUS, [Patrick] was able to squeeze out even more runtime by dismissing the boost converter from the design and driving the Pi directly from the battery voltage. If that worries you, you can either read a detailed explanation on why that works so well or just have a look at the more compliant 5 V version.
Eventually, [Patrick] used his module to create a Raspberry Pi time-lapse camera. A little script lets the Pi take a picture on boot up, set a wake-up timer and go back to sleep again. Safely enclosed in a waterproof electric box and deployed into the wild, the camera took 120 pictures on a single charge.
We’re sure the module will find it’s way into many cool projects and we’re counting the hours until we can get one in [Patrick’s] tindie store. Until then, enjoy the time-lapse video:
We can commiserate with [HardwareCoder] who would rather not leave his PC speakers on all the time. The Creative T20 set that he uses turn off when you turn the volume knob all the way down until it clicks. So shutting them off means repositioning the volume each time they’re switched on again. This hack kills two birds with one stone by turning on and off automatically without touching that knob.
The system is based around an ATtiny45 and a few other simple components. It uses two ADCs to monitor the rear input channels of the PC speakers. If no sound is detected for more than one minute, the shutdown pin of the speakers’ amp chip is triggered. That’s not quite where the hack ends. We mentioned it monitors the rear input of the speakers, but it doesn’t monitor the front AUX input. An additional push button is used to disable the auto-sleep when using this front input. There is also a fancy PWM-based heartbeat on an LED when the speakers are sleeping.
[HardwareCoder] was worried that we wouldn’t be interested in this since it’s quite similar to a hack we ran a few years ago. We hope you’ll agree it’s worth another look. He also warned us that the demo video was boring. We watched it all anyway and can confirm that there’s not much action there but we embedded it below anyway.
Continue reading “Auto-sleep Hacked in PC Speakers”
[Kyle Fredericks] tipped us about his first electronics project, a cheap and smart sleep mask that uses a vibration sensor to detect rapid eye movements.
As some of you may know, REM sleep is the part where you dream the most vividly and actively. If some external stimulation (sound, movement) is sent to you at this moment, it may help you take control of your dream by becoming aware of it. If not, your brain will create dream scenarios that incorporate this stimulus.
The interesting part of the concept is that the vibration sensor calibrates itself at the stage 2 sleep, when no eye movement occurs. This later allows a very accurate detection of the REM sleep stage, triggering a shelf stereo. Secondary buttons are even included in the mask sides.
[Kyle Fredericks] went to great lengths to document every step of the project, making it a perfect first step to learn electronics for beginners out there.
[Viktor] dredged up a hack he pulled off years ago. His grandfather likes to end the day in front of the TV, but he falls asleep soon after sitting down. Rather than tick away the electricity meter all night, [Viktor] built an automatic shutoff which is akin to a modern TV’s sleep feature.
At the time microcontrollers were not as easy to source as they are now. So [Viktor] used a circuit based on the 7400 family of logic chips. It uses a multivibrator to feed some binary counter chips. These are used to divide the oscillations to establish the desired timing. He tuned the system to be about 15 minutes, but that can be adjusted using a potentiometer built into the multivibrator. When time is about the run out an LED next to the TV comes on. This way if [Viktor’s] grandfather is still awake he can press a button next to his chair to reset the counter. But if he’s already snoozing the counter will eventually switch off the television.
This is the desktop binary clock which [Tim the Floating Wombat] recently finished building. He calls it the Obfuscating Chronoscope since it’s a bit more difficult to read than your traditional analog or digital timepieces. But the simple design looks neat and it’s a great way to learn about board layout and microcontroller code.
He started by solving a few questions about the display technique. He wanted to use as few LEDs as possible. He settled on just four, and to prevent unnecessary confusion, decided to make sure each type of display (seconds, minutes, hours) would have at least one LED on at a time. Hours are easy enough to display, but with just four bits how can minutes be shown? He uses a 5-minute resolution, always rounding up to the next division of five. This way the first bit will be illuminated on the hour.
A PIC 24F16KA102 microcontroller keeps time using its built-in RTC and a clock crystal. It puts itself into deep sleep mode after displaying the time. The black knob at the bottom is a push-button which resets the chip, waking it up just long enough show the time once again.
Here’s an effort to make a cheap lucid dreaming mask that is also comfortable. The idea is in response to the goggles we saw in April (which would not be too comfortable to sleep in) and the wildly successful Remee (which has an $80 target price).
The mask itself is sewn from a child’s fleece blanket. Inside is a piece of foam cut from some recreation mat. You know, those squares made for a play area that connect together like a jigsaw puzzle. You may have already spotted the Arduino in the image above, but the project is designed to run from an AVR chip embedded in the foam. The design only uses three LEDs, which may or may not work for you — we’d guess it depends on how they line up with your eyes. The video after the break does a great job of illustrating each point in the construction.
If you’re looking for something less soothing and more recreational you could always try out these trippy goggles.
Continue reading “Lucid dreaming mask marries economy with comfort”
This hardware is used to keep a computer monitor awake when there is motion in the room. The monitor displays important information for firefighter in the vehicle bay, but only needs to be on when they are getting ready to go out on a call. The solution is a simple one, a PIR sensor combines with a mouse for motion sensitive input. When the PIR sensor detects motion it causes a mouse button click via a 2N3904 transistor. Now the monitor will not waste power or have burn-in over the long term, but whenever someone is in the room it will be displaying the information that the emergency workers need to know.