Extremely Sensitive Magnetometer

A truly fascinating project, this super-sensitive dual-channel design detects magnetic field strength changes of as little as 3nT (nanoTeslas).

 

It is completely immune to stationary magnetic fields and has high immunity to magnetic noise. Separate handheld controller for sensitivity adjustment. It’s so sensitive that we’ve found it can find ferrous objects smaller than the head of a pin!

 

Easy to use, it has both a simple LED and relay switch output. Straightforward to build, using discrete through-hole components.

 

Useless Box

A take on the original ‘Useless Box’ electro-mechanical novelty, it’s a simple box with a switch marked ‘Do Not Switch Off’ – but what happens if you do switch it off?

 

It’s used along with our Super Digital Sound Effects Generator (PE, Aug-Sept 2019). A great Christmas gift or surprise for youngsters, for use under adult supervision.  This design uses two PIC microcontrollers requiring downloadable .hex files; the separate Sound Board is PICmicro based and also requires a downloadable .hex file.

The Useless Box uses standard discrete through-hole components but note that the Sound Effects Generator board is a miniaturised circuit using surface mount devices and good soldering  skills are required to complete it.

 

• More background information is at https://en.wikipedia.org/wiki/Useless_machine

 

Four–channel High-current DC Fan and Pump Controller

This multi-channel pump and fan speed controller can be used anywhere you need to adjust the speed of low-voltage DC fans or other PWM-controlled devices.

 

It is versatile and is easy to set up using an onboard USB interface. It provides both absolute or differential control, based on either the absolute temperature of one or two sensors, or the difference in temperatures between two sensors. Up to four NTC or digital sensors can be used. Four independent 10A MOSFET outputs provide 4 x 10A or 2 x 20A, or 2 x 10A and 1 x 20A output. Many uses in automotive and control technology.

Surface mount components are used throughout. Good soldering skills are needed to complete this project successfuly.

 

Colour Maximite Computer – Part 2

This month we cover the constructional details for building this retro 80s home computer. It contains surface mounted devices and good soldering skills are needed if you decide to assemble everything from scratch yourself. (Pre-populated boards are also available from micromite.org.)  This article provides all the information you need to identify parts and install them correctly. In Part 3 next month, we’ll explore some applications, including having some fun and retro games with your Maximite!

 

Using Stepper Motors (Part 3)

In this part we explore the essential electronics needed to drive stepper motors efficiently, looking at driver circuitry for common types.

 

Audio Out

A plethora of practical hints and tips for building and using  loudspeakers are given this month, also examining the physics behind the moving coil itself and a detailed examination of common loudspeaker terminals and connection types. Plenty of hands-on advice and hints and tips for audio enthusiasts, not to be missed!

 

Also in this month’s issue:

 

• The Fox Report – an update on Huawei and Oppo, the latest Chinese smartphone maker hoping to hit the big time.
• Techno Talk – the implications of the expected changeover from analogue to VoIP telecoms.
• Net Work – Freeview channel anomalies; an inexplicable Ethernet port on an LG TV; the changing face of UK power consumption over the past 50 years; the unspoken features of smart meters.
• Circuit Surgery – common emitter transistor amplifiers examined
• Max’s Cool Beans -  Max eggs us on with more insightful news about the HRRG, or Heath Robinson Rube Goldberg 4-Bit Mixed-Technology Computer
• Make It with Micromite (Part 11): serial data communications

 

Next month

Digital Signal Processor; Zero-Risk Serial Link; Four-channel Fan and Pump Controller (Part 2); Colour Maximite Computer (Part 3); Using Stepper Motors (Part 4). Contents may be subject to change.

 

There’s more in PE than ever before! PE is packed with practical electronics projects and theory for the hobbyist. You can order a printed copy of PE for delivery to your door (worldwide), or try the PDF Version (needs Adobe Reader for Windows), or the Pocketmags for your mobile device. Subscribe now!

 

 

Source code file - 1219.zip

 

NEW SHOPPING CART NOW ONLINE!

 

Our new website and shopping cart will bring you a fresh new design together with modern navigation features. During a period of transition, areas of our current website will still be operating, so watch this space for more news in the next few weeks!

 

Our new Online Shop has been redesigned to bring you convenient new features along with a fresh new look. You can buy back issues, books, CDROMs and more, and we ship worldwide as before. You will now have access to order histories and file downloads.

 

Customers' existing details have been migrated to the new shopping cart so you should be able to log in as normal.

 

New Downloads Service

 

We're also modernising our Downloads service. Monthly source code .zip files will continue to be free but users will need to create an account in the Online Shop to access them.

 

Downloads will available in the Shopping Cart area and can be stored and accessible in a History section of your personal account, enabling you to keep track of them.

 

A limit of two downloads of any one .zip file is allowed, but don't worry, we'll always try to help out if you need another copy later down the line.

 

 

Visit the new PE Online Shop