OK some basics. the most important transformer formula is VT = NAB V = Voltage across the winding T = Time (s)(or us with mm2) N = Number of turns A = cross sectional Area of ferrite/alloy (m2)(or mm2 with us) B = Maximum flux swing of the ferrite/alloy ( in tessla) Any transformer/ inductor with a closed magnetic path ( no air gaps) will saturate once the VT product has been exceeded. What that means is the inductance will change from a very high value to a very low value probably 1000:1 ( very useful sometimes(google MPC CVL) not in this case. you can make pulse transformers easily unfortunately the one you want is either very large or quite slow. you said 80V * 144uS = 11520 if you use a value of 0.4T ( which is quite high but ok for something like 3c90) and a CSA of 100 t= (80*144)/(100/0.4)= 288 turns its quite a few to wind by hand and that's just the primary. you could use a CSA of 2880 and you'd only need 10 turns but .............. Also one other thing to remember with transformers is the average voltage must be zero. so your pulse generator may need a decoupling capacitor in series with the input of the transformer. Richard. ----- Original Message ----- From: "wayne" To: "'Microcontroller discussion list - Public.'" Sent: Saturday, January 08, 2005 9:34 PM Subject: RE: [EE] Transformer isolation problen > The output going in is lower than the unloaded output, but the output > driver > can provide the current.. As its clear my understand of transformer theory > is sadly lacking, have you any pointers? > > Wayne > > -----Original Message----- > From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf > Of > Richard Benfield > Sent: 08 January 2005 21:15 > To: Microcontroller discussion list - Public. > Subject: Re: [EE] Transformer isolation problen > > It'll take approx 100ns to saturate a transformer that small I guess > that's > > why you don't see much. > But to be honest I'm surprised you can see much going in either. Once the > transformer saturates its impedance becomes very low probably less than > 1R. > > Richard > ----- Original Message ----- > From: "wayne" > To: "'Microcontroller discussion list - Public.'" > Sent: Saturday, January 08, 2005 8:49 PM > Subject: RE: [EE] Transformer isolation problen > > >> ----Original Message----- >> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf >> Of >> Richard Benfield >> Sent: 08 January 2005 20:30 >> To: Microcontroller discussion list - Public. >> Subject: Re: [EE] Transformer isolation problen >> >> What's the Volts time product of the transformer and how long is the >> pulse >> on for? if its very low you wont see much but you should see some kind of >> spike. >> >> Transformer has Vus 8.5 the pulse is 144uS. The transformer is on the >> link >> below. >> >> > http://www.rapidelectronics.co.uk/rkmain.asp?PAGEID=80010&CTL_CAT_CODE=&STK_ >> PROD_CODE=M32367&XPAGENO=1 >> >> >> Can you see the pulse as it goes into the transformer? >> >> Yes. >> >> >> >> ----- Original Message ----- >> From: "wayne" >> To: >> Sent: Saturday, January 08, 2005 8:22 PM >> Subject: [EE] Transformer isolation problen >> >> >> Hi All, >> >> >> >> I have a circuit that generates a pulse at around 80V. I need to isolate >> it >> for various reasons. I am using a pulse isolation transformer, but the >> output of the transformer (its 1:1) is ziltch. And I being stupid ad >> missing >> something obvious? The pulse generator will generate 80v into 500 Ohms, >> so > >> I >> would expect at least some output from the transformer. >> >> >> >> Wayne >> >> >> >> -- >> http://www.piclist.com PIC/SX FAQ & list archive >> View/change your membership options at >> http://mailman.mit.edu/mailman/listinfo/piclist >> >> >> -- >> No virus found in this incoming message. >> Checked by AVG Anti-Virus. >> Version: 7.0.300 / Virus Database: 265.6.9 - Release Date: 06/01/2005 >> >> >> -- >> No virus found in this incoming message. >> Checked by AVG Anti-Virus. >> Version: 7.0.300 / Virus Database: 265.6.9 - Release Date: 06/01/2005 >> >> >> >> >> -- >> No virus found in this outgoing message. >> Checked by AVG Anti-Virus. >> Version: 7.0.300 / Virus Database: 265.6.9 - Release Date: 06/01/2005 >> >> >> >> -- >> No virus found in this outgoing message. >> Checked by AVG Anti-Virus. >> Version: 7.0.300 / Virus Database: 265.6.9 - Release Date: 06/01/2005 >> >> -- >> http://www.piclist.com PIC/SX FAQ & list archive >> View/change your membership options at >> http://mailman.mit.edu/mailman/listinfo/piclist >> >> >> -- >> http://www.piclist.com PIC/SX FAQ & list archive >> View/change your membership options at >> http://mailman.mit.edu/mailman/listinfo/piclist >> >> >> -- >> No virus found in this incoming message. >> Checked by AVG Anti-Virus. >> Version: 7.0.300 / Virus Database: 265.6.9 - Release Date: 06/01/2005 >> >> >> -- >> No virus found in this incoming message. >> Checked by AVG Anti-Virus. >> Version: 7.0.300 / Virus Database: 265.6.9 - Release Date: 06/01/2005 >> > > > > -- > No virus found in this outgoing message. > Checked by AVG Anti-Virus. > Version: 7.0.300 / Virus Database: 265.6.9 - Release Date: 06/01/2005 > > > > -- > No virus found in this outgoing message. > Checked by AVG Anti-Virus. > Version: 7.0.300 / Virus Database: 265.6.9 - Release Date: 06/01/2005 > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > > > -- > No virus found in this incoming message. > Checked by AVG Anti-Virus. > Version: 7.0.300 / Virus Database: 265.6.9 - Release Date: 06/01/2005 > > > -- > No virus found in this incoming message. > Checked by AVG Anti-Virus. > Version: 7.0.300 / Virus Database: 265.6.9 - Release Date: 06/01/2005 > -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.300 / Virus Database: 265.6.9 - Release Date: 06/01/2005 -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.300 / Virus Database: 265.6.9 - Release Date: 06/01/2005 -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist