I am designing a PCB consisting a microcontroller in which I have to ensure that I have removable crystal . I am looking for a female connector in which I can easily plug/unplug/swap the crystal (usually has two outputs). I am designing the system using Eagle, however, I've had no luck finding a suitable connector. I believe there are a lot of female connectors available but I do know that there are some specifically designed to hold crystal. Is there an Eagle library consisting these holders? Can someone point me to the right eagle library?
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1\$\begingroup\$ Crystals are typically not designed to be hot-swappable. You usually pair crystals with small-value (a few pF) capacitors to stabilise them, and these are chosen for a given crystal. The tracks leading to and from the microcontroller also need consideration when used with a given crystal, as they contribute stray capacitance. I'd be surprised if there are sockets available specifically for crystals. \$\endgroup\$– SeanCommented May 2, 2019 at 16:15
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1\$\begingroup\$ You're probably going to have to design your own footprint. Before synthesizers were common crystal holders were often found in radio receivers. There may still be part numbers out there you can use. If not, a Mil-Max style single-pin socket designed for the diameter of the crystal pins would work. Keep in mind that a crystal designed to be soldered into a board isn't going to stand up well to plugging and unplugging. \$\endgroup\$– TimWescottCommented May 2, 2019 at 16:39
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1\$\begingroup\$ Pluggable crystals are a thing. You used to be able to buy CB walkie talkies, and buy the crystals for just the channels you wanted to use. My dad had a pair like that back in the 1970s. Motorola also produced professional two-way radios with pluggable crystals to select the frequency. Check out the MX300. \$\endgroup\$– JRECommented May 2, 2019 at 16:49
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2 Answers
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Some microcontroller evaluation boards employ machined pin sockets that take a HC-49U type crystal. These socket pins seem to be very similar to high-quality dual-inline-package (DIP) pins. These socket pins can be purchased individually.
BUT notice that the crystal has a metal case, and requires a non-conductive gasket between crystal bottom and socket, otherwise the crystal's metal case can short out to the socket. In the photo, the un-plugged crystal gasket is white. Crystal socket pins are gold-coloured. The other 8 MHz crystal is soldered into the board.
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I have just used 2 pins from a machine socket strip like this. Didn't seem to be any worse than crystal plugged into a breadboard. The pins are sunk into the plastic housing enough to isolate the pins from the case.
