Save Your Back by Using a High Desk March 14, 2008
Sitting actually puts a lot strain on your lower back. Over the years, working at a desk job can really injure your back so that you won’t be able to sit comfortably for extended periods of time anymore. After suffering such an injury myself, I found that the only way I could get back to work was to use a desk high enough to stand at while working. I also have a chair that is high enough so I can alternate sitting and standing. Even if you end up sitting most of the time as I do these days, it is still well worth it.
Most modular office furniture can be (more…)
Schematic and PCB Design Process March 7, 2008
Question:
I would like to know how a circuit designer in OrCAD plans the schematic and layout for the digital, analog, power, low speed high speed portion of the PCBs?
Answer:
Wow, this is a big but good question! For anyone considering undertaking a schematic capture and PCB layout for the first time, it can seem like a daunting task. A modern PCB serves not just as a means to interconnect components, but also as a mechanical structure, heat conductor, noise shield, and even as a circuit element, and must go through a complex automated manufacturing process to boot.
Perhaps it is best to start with (more…)
3-Phase Calculations January 5, 2008
Here is a Zoho Sheet to do various 3-Phase calculations. It can convert between line-to-line and line-to-neutral voltages, find current based on apparent power (KVA), and choose the required wire cross sectional area to meet the target voltage drop. When designing such a system, you must also meet all applicable laws and safety codes.
It is embedded below (more…)
Wire Parameter Calculator September 20, 2007
This Javascript web calculator will calculate the resistance and ampacity for copper wire based on the gauge. Both metric (mm) and American Wire Gauge (AWG) are supported. Note: Ampacity is based on a curve fit to MIL-STD-975. To see the wire table that this calculator is based on as well as important information about wire insulation temperature ratings, click here.
Features:
- Results update as you type
- Several choices of units
- Units and other settings are saved between sessions
- Blog format allows user comments
Inputs:
| Wire Size |
Optional Inputs:
| Wire Temperature | Deg. | |
| Wire Length | ||
| Number of Wires in Bundle |
Results (per each wire):
| Resistance | Ohms | |
| Single Wire Ampacity | Amps | |
| Wire Bundle Ampacity (per wire) | Amps | |
| Copper Diameter | ||
| Copper Area | ||
| Copper Weight |
Hex, Decimal, and Binary Converter June 29, 2007
This web calculator converts numbers between the hexadecimal (hex), decimal, and binary formats. The calculator was designed to allow easy conversion between any of these three formats. This task is very common for those working with digital hardware and software including microcontrollers, DSP’s, FPGA, etc. (more...)
Skin Effect Calculator June 18, 2007
Electrical current always flows in the path that results in the lowest expenditure of energy. At lower frequencies, current flows in a path that reduces I^2*R losses. This is the path of shortest distance and is fairly intuitive to think about.
At higher frequencies, things get a little strange. (more...)
Four-Layer High-Speed PCB Design May 29, 2007
When minimum cost and high-speed are required, a four-layer board may be the answer. High-Speed PCB design generally requires controlled impedance traces and good power and ground planes in order to meet signal integrity and power integrity requirements. Four-Layer PCBs are essentially made of 2 two-layer hardboards “glued” together with a pre-preg spacer in between them. The thickness of the pre-preg is not as well controlled as that of the hardboards. So, for good controlled impedance traces, it is recommended to use the layers separated by hardboard as signal and ground. The layers separated by pre-preg can be used as power and ground.
Thus, a recommended stack up for a high-speed four-layer board is; (more…)
PCB Stack-Up Design And Impedance Calculator May 12, 2007
Review: A new PCB stack-up design and impedance calculator is available for download from Istvan Nagy (see link below). It is a full-featured Excel-based tool that helps plan the PCB stack-up so that controlled impedance traces can be effectively implemented. It covers both single-ended and differential traces and is based on the equation s from IPC-D-317A. It allows one to see the range of impedances that are possible for a given layer stack-up. It also has pre-distortion calculations to support high-speed compensation, a unit changer, and a materials library.
Right-Click, Download and Save the Excel tool here:
layerstack_planningoriginalipc.xls
Istvan Nagy’s home page:
[Sorry, link had to be removed due to content issues.]
Do you have a favorite stack-up and impedance calculation tool? Let us know about it in the comments below.
Effects Of Corners In PCB Traces April 6, 2007
A novel SPICE simulation technique was developed to investigate the effects of corners in PCB traces. The PCB traces were modeled by breaking them down into tiny squares or finite elements. A SPICE sub-circuit was made for the finite element and a small square symbol with one pin on each face was also created for it. Many such symbols were then placed in a schematic (like tiles) to graphically and electrically represent a PCB trace. A comparison was then done between a straight trace, one with a 90 degree square corner, and another with a 90 degree corner beveled at 45 degrees. (more…)
Transmission Line Calculator March 6, 2007
The Excel based tool (see link below) calculates the capacitance and inductance per unit length as well as the impedance of a transmission line. It may be applied to wires, PCBs, etc. (more…)
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