UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Other Discussions > Homebrew Equipment

Notices

Homebrew Equipment A place to show, design and discuss the weird and wonderful electronic creations from the hands of individual members.

Closed Thread
 
Thread Tools
Old 23rd Sep 2020, 3:25 am   #41
Uncle Bulgaria
Nonode
 
Uncle Bulgaria's Avatar
 
Join Date: May 2016
Location: Cornwall, UK.
Posts: 2,315
Default Re: Bat Detector with Knowles Ultrasonic microphone problems

Some progress with the split supply. The signal generator is attached to VGND and IN, at 40kHz. I have only my remaining LM358 in place, acting as the unity gain stages. First picture is the output of the first LM358 with the split supply, on pins 1 (Inverting stage, upper trace) and 7 (non-inverting, lower trace). The second shows the split supply disconnected.

The only downside is that they're not inverted compared to each other!

I can now see Peter's point that the supply is referenced to 1/2 Vcc on the microphone board. Why that is not carried through, as the trace suggests, I don't know.
Attached Thumbnails
Click image for larger version

Name:	LM358 Split Supply.jpg
Views:	42
Size:	55.2 KB
ID:	216220   Click image for larger version

Name:	LM358 single supply.jpg
Views:	39
Size:	46.8 KB
ID:	216221  
Uncle Bulgaria is offline  
Old 3rd Oct 2020, 2:15 pm   #42
Uncle Bulgaria
Nonode
 
Uncle Bulgaria's Avatar
 
Join Date: May 2016
Location: Cornwall, UK.
Posts: 2,315
Default Re: Bat Detector with Knowles Ultrasonic microphone problems

I've got some output in the headphones, so I'm pushing on to make it up on veroboard. In the end, I've got some of the original author's ICs as I was rounding up a Farnell order. I'm going to make two detectors - one 5V and one 3.7V.

Has anyone any bright ideas for attaching the microphone board to the enclosure? I'm using one of those Hammond die-cast ones, intending to drill a tiny hole to coincide with the mic. I suppose I ought to glue the little mic board to the inside of the enclosure, but then I considered that the holes for the wires come through and would short out. Perhaps a mica sheet in between? Fish paper? Would either of these attenuate the ultrasonic signals?
Uncle Bulgaria is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 8:46 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.