X-Authentication-Warning: delorie.com: mail set sender to geda-user-bounces using -f X-Recipient: geda-user AT delorie DOT com X-ASG-Debug-ID: 1518791527-0ea5c173222f74de0001-9re8WH X-Barracuda-Envelope-From: gheskett AT shentel DOT net X-Barracuda-RBL-Trusted-Forwarder: 204.111.2.25 From: "Gene Heskett (gheskett AT shentel DOT net) [via geda-user AT delorie DOT com]" X-Barracuda-RBL-IP: 204.111.64.149 X-Barracuda-Effective-Source-IP: n64s149.fttx.shentel.net[204.111.64.149] X-Barracuda-Apparent-Source-IP: 204.111.64.149 To: geda-user AT delorie DOT com Subject: Re: [geda-user] (Off-topic) Question wrt driving HV piezo transducer Date: Fri, 16 Feb 2018 09:32:17 -0500 X-ASG-Orig-Subj: Re: [geda-user] (Off-topic) Question wrt driving HV piezo transducer User-Agent: KMail/1.9.10 (enterprise35 0.20100827.1168748) References: <1a5665d2-c032-29f3-6de3-d4e3cd52f42b AT linetec DOT nl> In-Reply-To: <1a5665d2-c032-29f3-6de3-d4e3cd52f42b@linetec.nl> X-KMail-QuotePrefix: > MIME-Version: 1.0 Content-Type: Text/Plain; charset="utf-8" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <201802160932.17130.gheskett@shentel.net> X-Barracuda-Connect: smtp2.edbg.cloud.shentel.net[204.111.2.25] X-Barracuda-Start-Time: 1518791527 X-Barracuda-URL: https://172.26.193.44:443/cgi-mod/mark.cgi X-Virus-Scanned: by bsmtpd at shentel.net X-Barracuda-Scan-Msg-Size: 3666 X-Barracuda-BRTS-Status: 1 X-Barracuda-Spam-Score: 0.50 X-Barracuda-Spam-Status: No, SCORE=0.50 using global scores of TAG_LEVEL=1000.0 QUARANTINE_LEVEL=1000.0 KILL_LEVEL=6.0 tests=WEIRD_PORT X-Barracuda-Spam-Report: Code version 3.2, rules version 3.2.3.47983 Rule breakdown below pts rule name description ---- ---------------------- -------------------------------------------------- 0.50 WEIRD_PORT URI: Uses non-standard port number for HTTP Reply-To: geda-user AT delorie DOT com On Friday 16 February 2018 06:38:48 Richard Rasker (rasker AT linetec DOT nl) [via geda-user AT delorie DOT com] wrote: > Hello Marcel, > > Op 16-02-18 om 06:32 schreef mhx AT iae DOT nl: > > On 2018-02-15 23:02, Richard Rasker (rasker AT linetec DOT nl) [via > > geda-user AT delorie DOT com] wrote: > > [..] > > > >> However, this afternoon, the product dealer was kind enough to send > >> me the schematic of a 500 Vpp development driver kit, featuring a > >> center-tapped symmetrical push-pull transformer(*) circuit with two > >> FDD16AN08 MOSFETs, each with a 1 uF capacitor across drain-source. > >> These big DS-caps seem rather weird already. > > > > [..] > > > > This could be a push-pull parallel-resonant parallel-load type > > configuration. > > It should be tuned to exactly the resonance of the effective L+C and > > will have > > a Vds of about 3.14159 times the supply voltage. The transistors > > turn on when > > their Vds tries to go negative (automatically). The 1uF across drain > > source does > > not sound familiar but is equivalent to a single cap between the two > > sources, > > i.e. in parallel to the transformed transducer (as it should be). > > Theoretically, this is the dual circuit to the HB series resonance > > series load > > one. > > Thanks for the explanation, although I don't quite grasp the > theoretical basis -- I'm not very experienced with transformer > circuits, and this one in particular still raises some questions. Can > you point to some other examples where this principle is used? Most > CFL drivers I find employ some sort of series resonance solution, > AFAICT, without any DS caps. > > For all clarity, I attached the schematic, also because there's > something else I don't understand: the top MOSFET (Q1) doesn't get the > burst frequency at all, just the 1.5 ms LF pulses. The bottom one (Q2) > is supplied with the burst signal as expected. > > I carefully checked this against the schematic I was given, and I'm > positive that I didn't make a mistake here. Could this be a mistake on > behalf of the original designer? I contacted the supplier, but they > couldn't tell me anything. Or perhaps Q1 is 'automatically' syncing to > Q2 via changing voltage levels on the drain? I can't really see this > happening in any reliable way... > > BTW, the circuit isn't really designed for resonance, as the 41 kHz > given is in reality a selectable frequency between 3 kHz and 300 kHz, > with 41 kHz being just one of the settings. > 41 kilohertz is the frequency used by older burglar alarms. But they ran a continuous tone, and detected the change in the rooms standing waves that a body moving around caused. I have Carhart notches 120+ db deep in both ears, but those things give me a tight feeling in both ears, annoying enough that I've been known to vacate the area w/o making a purchase. So I wouldn't be surprised to see a similar piezo device used here. The are also lots of ultrasonic parts cleaners that run at that frequency, altho I faintly recall one that claimed 90 kilohertz I saw recently, a 1/2 gallon model IIRC. Since a custom unit would cost more, 41 kilohertz is probably the sweet spot priced unit. > Anyway, thanks for all your help so far (from the others too), I'm > learning a lot! > (And I think I'd better start calculating, building and measuring > things now.) > > Best regards, > > Richard -- Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page