Electronic – How to mount a PCB in a project box

hobbyistpcb

Hi nearly finished my first electronics project and I need to think about how to mount it into a box.

I feel like I am missing something absolutely obvious with how to use PCB spacers.

Here is a picture of my box:

Here is a picture of some plastic PCB spacers:

The question is how to mount those spacers into the box so they don't fall out?

Should I glue them?

Should I drill holes in the box and then screw through from the other side of the box?

Any other method?

I have also looked at the spacers with sticky pads on the bottom but I prefer to reduce the risk of the PCB falling off at some point especially as the PCB is connected to a security system.

I appreciate this must be very obvious and lots of people are doing it every day but I would appreciate some direction on how to achieve this.

Best Answer

I like to choose project boxes that have a smoother inside bottom surface than the one you show in your picture. Those specialized mount points can get in the way of trying to use the standoffs that you show.

With that said the best strategy is to get a box that has molded in standoffs. Then you specially design your PCB to have mounting holes that match these standoffs.

However if you are making a prototype or one-off hobby project then I can suggest doing as I have. I drill holes through the bottom of the box in the correct locations to mount the type of standoffs as you show. These holes are then countersunk with and a flat head machine screw inserted from the outside is used to secure the nylon standoff on the inside. If you do not plan to remove these screws for disassembly the it is possible to back fill the screw head counter sink with epoxy provided the screw head is below the outside surface on the bottom side.

Related Solutions

Design of basic PCB

Generic pin headers are in the "pinhead" library. For something like the breakout board with multiple rows of headers, you can just place them in the proper locations on the board layout.

That said, do you even need to create a PCB? Since everything is on .100 inch centers, you could just get a protoboard, and solder your connectors on with point-to-point wiring.

If you want to go to the trouble and expense of making a proper PCB, you may want to consider starting from the Fio design files and integrating the motor driver on-board. The connections will be more secure, and you will save the mass of the extra PCB.

Electronic – Adequate decoupling / noise reduction for two accelerometers

The datasheet describes device as very well noise immune one with ratiometric (to power supply) output from DC to 400Hz. So to read DC "ratio" well, try use 2+2+2=6 wire "drive" "sense" cable for 2 devices. At DC you are affected by ohmic, galvanic, thermoelectic forces, but not the radio.

-- Drive --->--*-----+----------------------------+
-- Sense ---<--/     |                            |
                     |                            |
-- Sense ---<----Device (of DC half bridge type),Device--->---Sense--
                     |                            |
-- Sense ---<--\     |                            |
-- Ground --<--*-----+----------------------------+

All 3 sense wires should meet ratiometric input of ADC, say top goes to positive reference input of ADC, middle into positive input, bottom sense goes into 2 pins: negative reference (of balanced input) and negative pin of input.

Edit: Other thought. If there is movement on flexible cable, think about "triboelectricity". If cable friction, hit, vibration is an issue, then read specs about correct impedance of load. If this is high impedance, then add differential "line drivers" with current loop output and match a type of ADC to be "current ADC". Or better add small ADCs on board itself.

Best Answer

Related Solutions

Design of basic PCB

Electronic – Adequate decoupling / noise reduction for two accelerometers

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