Current Sensor Makes Intriguing Use Of Concrete

Getting a product to market isn’t all about making sure that the product does what it’s supposed to. Granted, most of us will spend most of our time focusing on the functionality of our projects and less on the form, fit, or finish of the final product, especially for one-off builds that won’t get replicated. For those builds that do eventually leave the prototyping phase, though, a lot more effort goes into the final design and “feel” of the product than we might otherwise think. For example, this current sensor improves its feel by making use of cast concrete in its case.

The current sensor in this build is not too much out of the ordinary. [kevarek] built the sensor around the MCA1101-50-3 chip and added some extra features to improve its electrostatic discharge resistance and also to improve its electromagnetic compatibility over and above the recommended datasheet specifications. The custom case is where this one small detail popped out at us that we haven’t really seen much of before, though. [kevarek] mixed up a small batch of concrete to pour into the case simply because it feels better to have a weightier final product.

While he doesn’t mention building this current sensor to sell to a wider audience, this is exactly something that a final marketable product might have within itself to improve the way the device feels. Heavier things are associated, perhaps subconsciously, with higher quality, and since PCBs and plastic casings don’t weigh much on their own many manufacturers will add dummy weights to improve the relationship between weight and quality. Even though this modification is entirely separate from the function of the product, it’s not uncommon for small changes in design to have a measurable impact on performance, even when the original product remains unmodified.

Thanks to [Saabman] for the tip!

20 thoughts on “Current Sensor Makes Intriguing Use Of Concrete

  1. Isn’t fresh concrete highly basic ? I’m not sure that’s a good substance to be placed in contact with traces on a PCB, or any electronic component. I know concrete is cheap but wouldn’t some type of resin be a better choice ?

      1. You’re right of course, transporting unnecessary weight is irresponsible and a crime against the environment and of course the unborn children of the world. Here in the UK we punish this sort of behaviour very severely and are considering bringing in laws to require people to remove their shoes whilst driving to work so that the extra weight of footwear (totally unnecessary whilst in an SUV) doesn’t add to the destruction of the earth. Perhaps you might consider this. Also, you are absolutely spot on about concrete and its environmental impact. Wattle and daub is much more sustainable but, unfortunately, we have found that it tends to be a little unstable when used for buildings more than 2 feet high. Also there is the problem of rain.
        Thank you for bringing your prognostications to a wider audience who, I am sure, will appreciate it as immensely as I do.

          1. As The World Burns – isn’t that an old soap opera? I think I’ll drive the Escalade down to Walmart and pick up a six pack to drink while watching it!

  2. This is a pretty cool trick, to be able to compete with the older inherently heavy technology that some people insist is better, but I think a better way to go is just to make things smaller, so they don’t get judged on weight the same way in the first place.

    A lot of stuff is bigger than it needs to be!

  3. I’ve seen a number of commercial products that use either concrete or plaster, for one of two reasons: 1) to make it feel more substantial and increase its perceived value (which seems to be the case here), or 2) to add cheap mass to make it more stable. For example, many washing machines use either bolted-on cast concrete pieces or concrete poured into cavities in plastic, to give the tub a higher moment of inertia, so that out-of-balance loads have less effect.

    Concrete is ideal for these purposes because it has relatively high mass density (kg/liter), and very low monetary density ($/kg).

    1. Most recent washing machines now cleverly use the fill water to add stabilising weight through a series of tanks that are empty when delivered – saving transport effort/energy – neat :)

      1. Cool! My knowledge of appliances is always outdated, because I only learn about them when they start breaking.

        I guess that water that the customer supplies is way cheaper than concrete, when you consider shipping! But seriously, how many years of people asking, “why are we shipping concrete in our products” did it take for someone to solve the problem?

        1. As with many things, it was probably a bit more complicated than just “don’t use concrete” given that it is significantly denser than water so, for the available volume, there’s more mass of concrete so more mass to stabilise against and less likely for the machine to hop around on high spin speeds.

          It could be that with all the microcontrollers and better motor control systems, it’s only more recently that washing machines are able to better measure how out-of-balance a load is (and either not spin as fast or try to re-distribute the items in the wash to a better balance) which means that the attached mass, for dampening purposes, no longer needs to be as significant, which means either a smaller concrete/metal block or, it’s now feasible to use a water filled volume.

  4. Uh, the MCA1101 is not rated for 4kV isolation; it is rated for a 4kV dielectric withstand test voltage and 400V operating voltage – Product Safety engineers typically call this ‘working’ voltage.

  5. I like the idea. One thing I hate deeply is when I am holding something with one hand and try insert cable with another, the damn device just moves further on the table :/ or some chinese radio with buttons in front and the device falls over if not used with two hands.

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