Awesome project from the Technoblogy blog:

Frequency Probe

The Frequency Probe is a handheld tool designed to help you debug your circuits by giving a visual indication of the frequency or voltage at the probe. For a periodic waveform it gives a digital readout of the frequency, with a range of about 1Hz to 5MHz and an accuracy of better than 0.3%. For a voltage level it gives a readout of the voltage:

The obvious way to implement a frequency meter is to count the number of pulses within one second; this then directly gives the frequency. I refer to this as Frequency Mode. The disadvantage of this method is that a long sample time is needed to measure low frequencies accurately.

The other way is to measure the interval between two pulses of the input signal; the reciprocal of this then gives the frequency. I call this Interval Mode. For example, if the interval between pulses is one second the frequency is 1Hz. The disadvantage of this method is that for high frequencies you need to measure the interval very accurately.

The ideal solution is to use Frequency Mode for high frequencies, and Interval Mode for low frequencies, which is the approach I’ve adopted with the Frequency Probe. I explain below how to calculate the best point at which to switch between modes.

I originally started work on this project a couple of years ago, but it turned out to be a lot trickier than I anticipated, and so decided to put it to one side. I revisited it earlier this year, and fortunately managed to solve all the issues.

Cabe Atwell writes on Hackster about Open Authenticator by Vedant Parajape which uses an ESP32 to secure data and features an OLED display, 300mAh LiPo battery, and a USB Type-C port for charging:

TOTP-Based Open Hardware Authenticator Powered by an ESP32 Microcontroller_

“I fired up google and tried to search about it, and surprisingly it used a pretty amazing concept. It had a shared key with the server, and then it did some computation on the shared key and current UTC time to get a 6-digit number. So, the remote device just had to be accurate at timekeeping,” Parajape noted in his project log. He then took that information and designed his initial Open Authenticator prototype using a development kit he had on hand and an ESP32 module. It worked well enough, but he wanted a more streamlined platform, similar to RSA’s SecureID Key FOB.

Some people like to use hardware authenticators or security keys when working with public or company computers to keep their data private, certainly so when hackers can easily steal unprotected information. There are many great authenticators on the market that can be had for cheap, but others such as developer Vedant Parajape have designed their own platforms using readily-available hardware. Parajape became interested in authenticators after seeing his dad’s security keys and wondered how they could generate code without being connected to a network.

.@ve0x10's Open Authenticator is an open source, TOTP-based hardware authenticator powered by an ESP32: https://t.co/wHuKIRA8ZR pic.twitter.com/rJTxLR5lxy

— Hackster.io (@Hacksterio) January 26, 2021

From Jo Hinchliffe on the Tindie blog:

Many DSLR camera’s have the ability to have their shutters triggered remotely, this is often useful for keeping the camera perfectly still, but if you can automate the triggering it’s perfect for time lapse photography. This interface sits between a Raspberry Pi and a range of DSLR cameras creating lots of time lapse possibilities.

It’s compatible with Octoprint Octolapse plugin which means that you can use a high end DSLR to create beautiful time lapses of 3D prints magically growing out of your printer bed. Also on the product page there are example python scripts that enable quick setup for high quality time lapse. We note that although it’s sold as a Raspberry Pi interface, this device is happy with a 3.3V or 5V input and that it could be triggered by most micro controllers. If you have a Sony, Canon or Nikon DSLR then this should work out of the box, for other DSLR you might need an audio adaptor to get up and running.

Looking around the marketplace there are other options for remote triggering cameras, this search for camera trigger reveals a plethora of interesting solutions. Sound triggers, lightning sensor triggers, stand alone intervalometer boards and more. We’ve also blogged on similar products previously, for example check out this camera interface kit that sets your camera up to be triggered by a laser pointer.