AC RMS AC is typically quoted as the AC RMS Voltage. E.g. UK mains voltage of 230V AC is 230V RMS. Peek AC Voltage Calculating the peek voltage of an AC RMS voltage: VAC * sqrt (2) Example: 230 V AC RMS * sqrt (2) = 325 V peek Example: 1500 V AC RMS * […]
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Screened Cables
Braided Screen Good strength and flex life (needed in applications with repeated cable flexing) Does work well at all frequency types but performs well and is recommended at low frequency to medium frequencies. Disadvantages Braided shield does not guarantee 100% coverage, typical 70% to 95% coverage (depends on how tight the branded formation is woven) […]
Flex PCB’s
General design tips Designing a flex PCB is no different to designing a regular PCB in terms of how you go about designing it. Corners Avoid using right angle corners, use curves, to reduce strain on the copper that could lead to it cracking Planes Avoid using solid copper regions, use cross hatch instead. Components […]
PCB Manufacture Options
Pads finish Standard tinned finish can be a bit uneven. Not an issue for lots of components, but can cause problems for some more specialist packages Gold plated finish option is really good when dealing with BGA, LGA, etc packages, where you really want a perfectly flat high quality finish to ensure the BGA package […]
Mosfet diode replacement
Mosfet providing polarity protection without diode voltage drop For a P channel mosfet, whenever the Gate voltage is lower than the (Source Voltage – Gate Threshold voltage) the MOSFET conducts. If the gate voltage is higher than this, it does not conduct. The greater the voltage difference from the Source the more the MOSFET can […]
Supressing back EMF
A simple way to think about inductive effects is to remember that the current in an inductor acts similar to the inertia of a mass, it wants to keep flowing, even after the voltage (force) across it it removed. It will keep flowing until all the inductive energy (1/2 LI²) is dissipated, which can generate […]
Propagation delay and PCB layout
Basic questions When do you need to start caring about matched net lengths etc? 100Mz to 200Mz is a good handwavy guide (but not necessarily!) How much propagation delay is added by PCB traces? 1nS of propagation delay is added to a signal for every 150mm / 6″ of PCB trace. Dielectric constant Varies between […]
SMS Messages
GSM Character Set SMS messages use a different character set to standard ASCII. Characters are 7bits and packed into 140 bytes, giving you up to 160 characters (7 x 160 = 1120 bits, 1120 / 8 bits per byte = 140 bytes). Conversion to and from various ASCII characters needs to be performed in code […]
Stress Testing Windows Computers
CPU stress test software Prime 95 https://www.mersenne.org/download/ Start test: Options > Torture TestStop test: Menu > Test > Stop Hardware monitoring of CPU load and CPU temperatures HWiNFO https://www.hwinfo.com/download/
ESD Testing (Electrostatic Discharge)
IEC 61000-4-2 / EN 61000-4-2 This is the basic immunity test method for personnel ESD and is often called up as a basic test method by immunity standards listed under the Electromagnetic Compatibility (EMC) Directive. ESD Simulator tips Direct contact ESD discharge – Pointed tip 4kV typ test voltage. Put tester in contact with a […]