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My current project involves embedding an MPU6050 accelerometer into straps, one of which goes below the knee, the other above the knee.

I need to fit the sensor into the strap and currently i have 6-core multi-threaded wire soldered directly into the board. This doesn't facilitate the greatest of long term stability, as too much strain and the wires will just pull out and break.

What I am wondering is if it is OK to:

  1. cover the wire side of the board in glue from a hot glue gun? Would this have any possible conductivity issues or risk damaging the wires or board itself?
  2. If it is OK to use the hot glue, would it be possible to cover the entire MPU6050 in the glue without compromising performance. This would leave me with a really solid sensor for embedding if so!

Any answers to the above questions would be greatly appreciated and I would be extremely grateful for any alternative options as well. I would like to keep the wires soldered into the board as it is extremely tidy and makes for easier embedding than if I were to use another connector.

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1) I do not see any problem here - I myself used hot glue to fix and isolate power source of robot from the copper side. It does not leak any (measurable by my tools) current, does not show any sign of detorations and works well both electrical and mechanical way. I used it only on copper side, where was risk of shortcuts and where were no heat dissipators (as it isolate also heat). But I think, that the MPU does not generate so much heat, to be worry about - body proximity and weather on summer would affect it more.

2) Hot glue is not as hot as soldering lead/tin so short contact with the MCU should not harm it. (You can shortly touch hot glue to manipulate it and not get burned, so it is not so hot). Anyway I would apply it as fast as possible and would leave it cool down before swithing it on (the working and the storing temperatures are different case). Be carefull with the wires, as the isolator can be melted, if heated by hot glue and moved at the same time. Also take in mind, that the hot glue should be little around the whole, to isolate from humidity. And that it would be complicated to solder anything after the glue is applied - so have all contacts (you may possibly need access) somehow lead out of the glue. And try the construction before applying the glue, to be extra sure, that nothing is missing and everything works.

I personally would place the MCU on some kind of PCB and solder the wires to the PCB organized the way the wires would continue to form "cable" and to have extra sure there is no force on the connection of MCU pins. Also I would fixed the whole cable to the PCB with something, so the solder itself is not under any force, as it is the most probabely place to broke there. An I would ensure, that the cable goes smoothly away from the PBC, as it would be bad, if it would be bent ower sharp edge at the place where it leave its glue support.

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  • Brilliant response! Thanks so much! Regarding your last point, I was thinking the exact same. A small pit of pcb will provide me with somewhere to attach the MPU6050 but also to possibly have some sort of restraint on the cable, to, as you mentioned, take the force off the solder joint itself. Thanks again! Jan 10 '17 at 16:42
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Would this have any possible conductivity issues

Nope.

or risk damaging the wires or board itself?

Nope.

If it is OK to use the hot glue, would it be possible to cover the entire MPU6050 in the glue without compromising performance.

Sure.

This is known as "potting". You can get special potting compounds, but hot glue is just as good.

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  • Thanks man! Would there be any chance that I could melt off the insulation on the wiring in doing this. Or would there be a special (maybe low temp) glue gun I should use? Jan 10 '17 at 16:03
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    The melting point of hot glue is considerably lower than the insulation of the wire.
    – Majenko
    Jan 10 '17 at 16:06
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    @EoinClancy just avoid touching the wire directly with the glue gun tip, even if even this should not melt the insulation
    – frarugi87
    Jan 10 '17 at 16:20

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