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HomeElectronicsCoin/button-cell holders could be practical, dependable, and even elegant

Coin/button-cell holders could be practical, dependable, and even elegant


Over time I’ve changed coin- and button-cell batteries in numerous merchandise and have needed to repair or enhance the marginal battery holders utilized in lots of them. It’s comprehensible however irritating that many low-end merchandise use cell holders with an absolute minimal of electrical-contact and mechanical-attachment floor space, which isn’t good for long-term reliability in addition to resistance to regular wear-and-tear.

The cell holders for these merchandise are sometimes simply stamped metallic items for the PC board. They connect with the battery backside for one contact and the highest (or edge rim) for the opposite, Determine 1. Each time you take away and substitute the battery, you place stress on the tiny contact space between the metallic stamping and the board.

Determine 1 Coin cell holders are sometimes simply primary stamped-metal contacts soldered on to the PC board. (Picture sources: diyleyuan.com, PCBoard.ca)

It could simply be twisted inadvertently twisted and ripped off, particularly when there’s little clearance to succeed in the battery and you must sort-of twist the contacts to do the removing and substitute. I’ve tried to resolder these minuscule contacts with blended success, since entry is proscribed, and the world is fairly tight.

Let’s face it, these stamped-metal battery holders are very cheap. Maybe the product producer assumes that the general product is so low cost that nobody will trouble to interchange the battery, which itself prices between $2 and $4. Perhaps, however perhaps not.

That’s why I act with warning after I want to interchange a coin or button cell in one in all these merchandise. If I see a type of low cost battery holders in there, I take it gradual and delicate with the battery removing and substitute.

However it doesn’t must be like this. There are many broadly accessible, pretty strong battery holders for coin and button cells accessible from many sources, together with ones with actual bases plus tabs to solder to the board; some actually have a retaining clip holding issues in place, Determine 2. Sure, they’re a number of cents extra and take a tiny bit extra room, however it might be good if even cheap merchandise used them…hey, we are able to all dream, proper?

Determine 2 Higher-quality cell holders embrace a discrete base for higher mechanical and electrical connections. Some actually have a top-side latch which retains the battery however could be launched for battery substitute. (Picture sources: West Florida Elements; MTI Company)

Generally, the battery holder is a supply of shock. I wanted to interchange the CR2032 coin cells in a small, cheap (~$25) Salter 2001 kitchen scale that’s at the least 20 years previous (and nonetheless accessible used at Amazon and eBay), Determine 3. As with most such scales, the unit is “closed up” pretty tight to take care of the mechanical integrity of the cantilever-weighing beam, load-cell, and platform meeting.

Determine 3 When it got here time to vary the batteries in cheap kitchen scale, I used to be anticipating an inexpensive battery-holder proper on the PC board.

I anticipated the batteries could be arduous to succeed in, however as an alternative they had been positioned below a small door on the underside. I opened that door not understanding what to anticipate for battery placement and connections, and assume it might an inexpensive, barely reachable association.

As a substitute, nonetheless, I discovered a really elegant strategy. The 2 coin cells had been in their very own considerably “elegant” detachable holder in a pocket away from the PC board, and linked to the board by a pair of modest-gauge wires so they’re considerably unbiased, Determine 4.

Determine 4 The 2 CR2032 batteries are in a detachable case.

This holder, in flip, had a totally detachable slide-out “drawer” which held the cells in place, making them simply accessible but full protected, Determine 5. All I needed to do was take the battery holder out of its pocket on the dimensions’s backside, slide out the drawer, take away and substitute the 2 cells, and reverse the process.

Determine 5 To take away/substitute the batteries, you merely slide their holder out from the case—really elegant in its personal small approach.

Not solely did it take only a few seconds for your entire course of, however there was no stress on the inner circuit board, because the wires between holder and board had sufficient slack. Whoever designed this scale and permitted the invoice of supplies (BOM) was considerate sufficient to make it simple but rugged, even when it added a number of cents to the BOM value—and I used to be grateful to that unknown designer or staff.

Too typically we see the place value pressures lead to a design, which is barely sufficient with respect to mechanical and thus electrical comfort and reliability, in client merchandise equivalent to these kitchen scales, low-end distant controls that come free with TVs, or different mass-market units. Usually, we pay the value, because the unit is tossed out too quickly when what needs to be an simply replaceable half isn’t. From an engineering perspective, after I see one which’s made “proper” with that little bit of additional consideration, I give silent shout out even whereas understanding they may by no means hear me.

Do you give the coin/button cell holder in your design a lot consideration or consideration? Have you ever ever used a barely higher and extra expensive half to realize a major improve in product life or person ease, solely to have your BOM ripped aside at overview by the fee staff? Had been you capable of make the case and win, or did a number of cents get in the best way of a extra practical and longer-lasting part or design strategy? Have typically needed to requested your self “what had been they considering right here?” or “why didn’t they select one other approach?”

Reference

Artwork Pini, Digikey, “The right way to Choose a Coin Cell Battery Holder for Most Shock and Vibration, and Ease of Alternative

Invoice Schweber is an EE who has written three textbooks, a whole bunch of technical articles, opinion columns, and product options.

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