I have a Ultrasound HC-SR04 unit which has tiny holes in each corner for screws/bolts. Can someone tell me the type/size of fixings I will need to attach it to my project? Thanks.
Can’t you measure the size of the holes with a ruler? Or caliper [(like this)?](https://www.sparkfun.com/products/10997)
Thanks for the reply.
Unfortunately I don’t have one of those. The holes are around 2mm in diameter, no bigger.
Since it is likely made in China I wouldn’t expect major precision in manufacturing tolerances anyway. So I’d say those are indeed intended to be 2 mm holes.
The one I have has holes which are 2.2mm in size measured with a caliper with 0.05mm resolution vernier scale (visual alignment of marks, non-digital readout). Large enough to fit a M2 screw into it easily. But some of the components are too close to them so I doubt a screw head or nut could fit on top of it without making conductive contact. Instead I just fixed it with hot-snot glue to a bracket made for it [like this one, but I didn’t want to be permanently fixed anyway. Alternatively I could have used ripties to secure it, but I didn’t have those at hand.
Measuring the distance between the most extreme inside edges of the holes on the long side I measure 44.3mm. Deducting one hole size from it I calculate the center of the holes to be displaced about 42mm on the long side.
Similarly on the short side the extreme inside edges of the holes are 19.3mm apart. Making the centers of it about 17mm apart on the short side.](http://www.banggood.com/Cartoon-Ultrasonic-Sensor-Mounting-Bracket-For-HC-SR04-Smart-Car-p-913714.html)