LCB710 – A nerd’s dream…

MicroCrystal RV-8803 – A Really Accurate RTC June 17, 2019- RTC chips traditionally were the domain of Maxim and NXP. Switzerland-based MicroCrystal recently made quite a buzz with its RV-8803, which offers simple integration, an I2C interface and extreme accuracy. Let us start out by looking at a system overview. Figure one shows how this I2C RTC is made up internally – interested observers note […]
Analog Devices’ LTM2887 – If a Digital Bus Needs Galvanic Isolation June 15, 2019- In theory, digital buses are intended to connect things to one another. Sadly, one sometimes wants but a logical connection – in many cases, galvanic isolation helps out. Should you ever feel like isolating very fast buses, definitely give the LTM2887 a chance. From a technical point of view, Linear Technologies attempt at entering the […]
AVAGO APDS-9008 or APDS-9005-020 – Keeping an Eye on Ambient Light June 14, 2019- Recent times saw quite a bit of interest for part numbers such as the APDS-9008 or APDS-9005-020 – they are a very interesting type of ambient light sensor. One of the oldest questions in regards to light sensors involves their spectral sensitivity. If a part is to output but one voltage level, the conversion between […]
STMicroelectronics’ LIS2DH12 – Low Power Motion Sensing June 12, 2019- Apple’s iPhone introduced gyroscopic sensors to a wider range – before that, accelerometers were not commonly found in consumer hardware. STM sells excellent parts which, however, get little media attention – time to take a look at the LIS2DH12. Integrating the part into your circuit as an MPU6500 alternative or MPU9500 alternative is not difficult. […]
Panasonic AMG8833 – FLIR for cheap June 7, 2019- FLIR made infrared thermal sensors cool – sadly, their parts are all but cheap (and suffer from export control problems). Panasonic’s Grid-EYE family is a low-resolution alternative which comes at significantly lower cost. From a technical point of view, Panasonic’s image sensor could not be simpler. We are looking at an 8×8 sensor with an […]
DipTronics DTS-62R-V – Small Switch, Very Big (and Very Cheap) June 5, 2019- When yours truly was but a lowly cadet, various US manufacturers produced (pricey but quite reliable) switches. Chinese vendors recently started to catch up – seeing the DTS-62R-V top our customer interest list shows that the run stage of the crawl-walk-run cycle is reached. DipTronics has been around the Asian switch market for ages, exhibiting […]

Controlling a large current with a small one without a physical connection…

Controlling a large current with a small one without a physical connection, traditionally leads to a knee-jerk reaction of relays. Optocouplers traditionally were limited to low currents.

For quite a bit of time, solid-state relays have been on the market. What once was a relatively large and expensive component is now available in comfortable six pin surface mount ICs – one example, which would have cost a lot a few years ago, is shown in the box below:

First of all, most solid-state relays, that includes the LCB710, are based on the principle of the optocoupler. This means that a small control current lights an LED, which then emits photons which trigger a set of photo transistors.

In the case of our part, the internal structure – as shown in the product data sheet – looks like this:

The two field effect transistors allow for AC and DC switching…

Very flexible!

One strength of traditional relays was that they did not give much of a fuss about what signal they were handling: once the switch was closed it – essentially – carried whatever you chased along it. Solid-state relays were problematic in this regard, as many of them could conduct current only in one direction. Fortunately, the component at hand does not have this problem.

Furthermore, the turn-on resistance is quite acceptable, with an average range of like 0.5 ohms. Forgive yours truly for reprinting the datasheet here – the following things are very very cool:

…Printing standard deviations in a datasheet is a surefire way to endear your product to this reviewer

One key benefit of solid state relays is their quick turn on time: in principle, you can expect turn-off in less than 2 ms, while activation is done about 0.75 ms in the worst case – in both cases, expect the majority of the parts to do significantly better, which can be seen as an invitation to select components by hand.
Finally, also keep in mind that performance is quite satisfactory: current of up to 1A can be controlled with 2mA. The galvanic insulation barrier is quite beefy, being able withstand to 3750 V RMS.

To select, or not to select?

An unverified rumour circulating in Eastern Europe claims that one of the reasons why Solartron went awry was their expensive selection process. Selecting parts provides a way to drive additional revenue to your company: selling prepared replacement parts is fun.

However, be careful; you need to hold additional stock and have quite a bit of labour costs. If you can design around it, to so by all means…especially as parts also change as they age…