Wireless power transfer has been around for a long time. The “crystal set” or “crystal radio” over 100 years ago used the power carried in the radio signal to produce sound without any amplification or receiving circuit power source. Early spark gap transmitters also used tuned wireless power transmission. Now the circuitry is more sophisticated […]
Supercapacitors: a good fit for the right niche
“Supercapacitors” (or electric double layer capacitors) have been around for a long time. Early uses were as an alternative to rechargeable batteries for retaining memory contents in domestic equipment. They were even made to look a bit like batteries in some cases, rather than electrolytic capacitors, such as these Panasonic RG series ones: This particular […]
How to measure current
If you want to measure the current taken by some circuitry, the normal way is to use a small resistance in the circuit and measure the voltage drop across the resistor. For AC currents, you can use a current transformer, but that is a bulky approach for AC applications. For DC current, particularly where you […]
Distortion tolerant (mostly): isolated digital interfaces
Following on from previous discussions on the problems of analog signal integrity and isolation, I came across the Linear Technology LTM2886 for isolation of SPI or I2C interfaces. This is one of a range of isolated transceivers from Linear Technology covering RS422, RS485, RS232, SPI, I2C and USB. A clear advantage of digital rather than […]
How to maintain analog signal integrity
We often discuss signal integrity in relation to digital data and communications — trying to ensure a high-speed digital signal isn’t corrupted during transmission— but analog signal integrity is also important. It could be simply trying to preserve the signal quality and accuracy within a PCB, or it could also cover the problem of transmitting an […]
Understanding Modulation and Mixing
Modulation is considered to be a radio frequency (RF) technique which refers to modifying a periodic waveform with another waveform. For example, frequency modulation takes an RF “carrier” signal (sine wave) at say 88MHz and varies the frequency slightly, based on your “modulating” signal which will most likely be an audio signal up to 15kHz […]
What are Hall effect sensors?
Magnetic sensors are typically Hall effect sensors (named after Edwin Hall who discovered the effect in 1879), whereby a small voltage difference can be measured across a conductor with current flowing through it when a perpendicular magnetic field is applied. They are available as small, integrated solutions with signal or multiple outputs, and analog or […]
How to achieve reverse polarity protection with ideal diodes
In battery operated devices which have removable batteries, you usually need to prevent the batteries from being connected the wrong way round to prevent damage to the electronics. If that is not possible by physical means you need to include some electronic protection. Physical protection can simply mean a polarized connector or a battery with […]
Going smaller & more portable with PCB embedded components
I recently came across the TDK SESUB-PAN-T2541 Bluetooth module. It is a complete bluetooth module consisting of a Texas Instruments CC2541 Bluetooth “System-on-Chip” (SoC) and the peripheral components required to use it – crystal, balun, and 15 other passive components. While it initially doesn’t sound that remarkable, when you look at the size (4.6mm x […]
Generating reference voltages
A “voltage reference” can mean anything from a simple resistive power supply rail splitter as a virtual ground for an opamp, to a high precision, low drift, low noise reference voltage for an analog to digital converter (ADC). For an opamp virtual ground, a couple of resistors and a capacitor can work and you may […]