Electronics “Mancave”: Small-Footprint Workspace

When it comes to a workspace, more doesn’t necessarily mean better. We encourage engineers and DIYers to focus their time and money on engineering, not on acquiring new and used equipment they’ll never use.

Belgium-based Jan Cumps has a very basic yet effective workspace. It is a true workspace. That means he actually has room to work there. It isn’t a cluttered room for storing junk.

Source: Jan Cumps

Source: Jan Cumps

Cumps noted:

I’m a clean-desker. Have to share it with studying kids. All gear has to have small footprint, or must be stow-away-able. That’s why you see a 4-in-1 multimeter, power supply, frequency counter and function generator, and a 2-in-1 hot air plus solder station. Components, meters, cables and what have you are stowed a way in boxes.

His equipment:

  • Philips MP 3305 oscilloscope
  • Metex MS-9150 4-in-1
  • Micronta (Tandy) and Metrix multimeters
  • Old-school soldering gear 
Share your space! Circuit Cellar is interested in finding as many workspaces as possible and sharing them with the world. Click here to submit photos and information about your workspace. Write “workspace” in the subject line of the email, and include info such as where you’re located (city, country), the projects you build in your space, your tech interests, your occupation, and more. If you have an interesting space, we might feature it on CircuitCellar.com!


Freescale High-Sensitivity Accelerometer Family

Freescale recently introduced a new range of three-axis accelerometers offering high sensitivity at low power consumption. According to Freescale, the FXLN83xxQ family is capable of detecting acceleration information often missed by less accurate sensors commonly used in consumer products such as smartphones and exercise activity monitors. In conjunction with appropriate software algorithms, its improved sensitivity allows the new sensor to be used for equipment fault prognostication (for predictive maintenance), condition monitoring, and medical tamper detection applications.

Source: Freescale

Source: Freescale

The 3 mm × 3 mm chip has a bandwidth of 2.7 kHz and uses analog output signals for direct connection to a microcontroller’s ADC input. Each chip has two levels of sensitivity that can be changed on the fly. The complete family covers acceleration ranges of ±2, ±4, ±8, and ±16 g, with gains of, 229.0, 114.5, 57.25, and 28.62 mV/g, respectively. Zero g is indicated by an output level of 0.75 V.

The FXLN83xxQ family:

  • FXLN83x1Q ±2 or ±8 g range
  • FXLN83x2Q ±4 or ±16 g
  • FXLN836xQ 1.1 kHz x- and y-axis bandwidth (Z = 600 Hz)
  • FXLN837xQ 2.7 kHz x- and y-axis bandwidth (Z = 600 Hz)

The sensors operate from 1.71 to 3.6 V (at 180 µA typically, 30 nA shutdown). The company has also made available the DEMOFXLN83xxQ evaluation break-out board with a ready-mounted sensor to simplify device integration into a test and development environment.

A Wire Is an Inductor (EE Tip #126)

I’m confident you know that you should keep wires and PCB tracks as short as possible. But I’m also sure that you will underestimate this problem fairly frequently.

Remember that 1 cm of a 0.25-mm-wide PCB track is roughly equivalent to an inductance of 10 nH. If this 10 nH is paired with, say, a 10-pF capacitor, that gives a resonant frequency as low as 500 MHz, which is easily below the third or fifth harmonics of the clock frequencies commonly seen on modern high-speed digital boards. Similarly, a 1-cm-long track will jeopardize the performances of any RF system such as a 2.4-GHz transceiver. There is only one solution: keep tracks and wires as short as possible. If you can’t, then use impedance-matched tracks.

Remember this rule especially for the ground connections: any grounded pad of any part working in high frequencies should be directly connected by avia to the underlying ground plane. And this via must be as close as possible to the pad, not some millimeters away.

Just yesterday I did a design review of a customer’s RF PCB. A small 0402 inductance was grounded through a via that was 3 mm away. It was a bad idea because the inductance was as low as 1 nH. Those 3 mm changed its value completely.—Robert Lacoste, “Mixed-Signal Designs,” CC25:25th Anniversary Issue, 2013. 

Prototyping for Engineers (EE Tip #111)

Prototyping is an essential part of engineering. Whether you’re working on a complicated embedded system or a simple blinking LED project, building a prototype can save you a lot of time, money, and hassle in the long run. You can choose one of three basic styles of prototyping: solderless breadboard, perfboard, and manufactured PCB. Your project goals, your schedule, and your circuit’s complexity are variables that will influence your choice. (I am not including styles like flying leads and wire-wrapping.)PrototypeTable

Table 1 details the pros and cons associated with each of the three prototyping options. Imagine a nifty circuit caught your eye and you want to explore it. If it’s a simple circuit, you can use the solderless breadboard (“white blob”) approach. White blobs come in a variety of sizes and patterns. By “pattern” I mean the number of the solderless connectors and their layout. Each connector is a group (usually five) of tie points placed on 0.1″ centers. Photo 1 shows how these small strips are typically arranged beneath the surface.Prototype p1-4

Following the schematic, you use the tie points to connect up to five components’ leads together. Each tie point is a tiny metal pincer that grips (almost) any lead plugged into it. You can use small wires to connect multiple tie points together or to connect larger external parts (see Photo 2).

If you want something a bit more permanent, you might choose to use the perfboard (“Swiss cheese”) approach. Like the solderless breadboards, perfboards are available in many sizes and patterns; however, I prefer the one-hole/ pad variety (see Photo 3). You can often find perfboards from enclosure manufacturers that are sized to fit the enclosures (see Photo 4).

There is nothing worse than wiring a prototype PCB and finding there isn’t enough room for all your parts. So, it pays to draw a part layout before you get started just to make sure everything fits. While I’m at it, I’ll add my 2¢ about schematic and layout programs.

The staff at Circuit Cellar uses CadSoft EAGLE design software for drawing schematics. (A free version is available for limited size boards.) I use the software for creating PCB layouts, drawing schematics, and popping parts onto PCB layouts using the proper board dimensions. Then I can use the drawing for a prototype using perfboard.

The final option is to have real prototypes manufactured. This is where the CAD software becomes a necessity. If you’ve already done a layout for your hand-wired prototype, most of the work is already done (sans routing). Some engineers will hand-wire a project first to test its performance. Others will go straight to manufactured prototypes. Many prototype PCB manufacturers offer a bare-bones special—without any solder masking or silkscreen—that can save you a few dollars. However, prices have become pretty competitive. (You can get a few copies of your design manufactured for around $100.)

There are two alternatives to having a PCB house manufacture your PCBs: do-it-yourself (DIY) and routing. If you choose DIY approach, you’ll have to work with ferric chloride (or another acid) to remove unwanted copper (see Photo 5). You’ll be able to produce some PCBs quickly, but it will likely be messy (and dangerous).Prototype p5-6

Routing involves using an x-y-z table to route between copper traces to isolate them from one another (see Photo 6). You’ll need access to an x-y-z table, which can be expensive.—CC25, Jeff Bachiochi, “Electrical Engineering: Tricks and Tools for Project Success,” 2013.

This piece originally appeared in CC25 2013