Just for Dexterslab2013 - Page 1
Forum section: electronics / general

author: SeanB
author_rank: Super Contributor
timestamp: September 28, 2014, 03:50:28 pm
content: Mark ( dexterslab2013) commented on a video I did on an old SCSI hard drive starting up. He said he had connected a contact microphone to one to record the acoustics better. This got me thinking, and i remembered these little vibration sensors I had picked up a while ago, but had never used.Lamerholm Electronics Ltd VP6 vibration sensor, now superseded by the VP7 sensor. Designed as a sensitive vibration sensor, with a 0BA mounting. So I got one out of it's little pill box, complete with it's calibration data of 91mV per 'g' at 70Hz, and a self resonant frequency of 17kHz mounted on a 100g steel block. Done 12 May 1978, so it has had 36 years of sitting unused on a shelf. Looked around and got an old low piezo cable, that was used on an oxygen sensor, and soldered it to the 2 lugs on the unit.So I recorded the startup, using this sensor and a cheap USB headphone interface from flEaBay that was a little more sensitive than the built in audio mic input. Recorded with Audacity, and saved as FLAc and MP3, but the MP3 is 1.8M, so not attachable here.

author: German_EE
author_rank: Super Contributor
timestamp: September 28, 2014, 04:59:41 pm
content: it looks like one of those things which seems pointless but good fun. I once had a very strange noise coming from a Saab 900 engine and the mechanic used a wooden stick to locate the source of the noise, one end went on the engine block and the other was jammed just behind his ear. With the engine turned off and manually rotated he could hear a loose bolt where one of the piston rods met the crank shaft.

author: SeanB
author_rank: Super Contributor
timestamp: September 28, 2014, 05:35:12 pm
content: Need to get a better amplifier for the pickup though, will probably pull out a matching Siemens valve amp to provide extra gain and drive. Must remember to get them out sometime and hook the lot up. Very low signal level, barely audible with the gain turned up full, had to equalise gain by a lot.

author: dexters_lab
author_rank: Unknown
timestamp: September 29, 2014, 07:21:06 am
content: neat!i just picked up one of these:http://www.ebay.co.uk/itm/400739141159so my father can try and listen for termites in wood, i might give it a go on a hard disk see what it's like

author: dexters_lab
author_rank: Unknown
timestamp: September 29, 2014, 07:33:04 am
content: an excerpt from Sean's original, 50% playback rate

author: dexters_lab
author_rank: Unknown
timestamp: September 29, 2014, 08:45:04 am
content: Quote from: German_EE on September 28, 2014, 04:59:41 pmyes, kinda pointless though there are those who search out odd noises like this to incorporate into synth samples/musicif i could get that damd floppy drive working on my kurzweil keyboard thats taking up WAY too much space at the moment we'd be able to have even more pointless fun

author: SeanB
author_rank: Super Contributor
timestamp: September 29, 2014, 07:34:34 pm
content: Mom used to have a Renault 5 ( yes I know, but it was economical on fuel, used a tank every 2 years) which had an annoying rattle inside the dash. Dad took that car to pieces, down to having no dashboard in it at all and only the steering wheel and pedals, but could not locate the buzz at 95kph. Best we could guess it was built into the vehicle shell at manufacture, and was a resonance of the thin firewall and the other panels. Never worried Mom, she never got above 40. Drove dad nuts, seeing as he was amongst others an automotive engineer.