----- Original Message ----- From: "David C. Partridge" <[EMAIL PROTECTED]> To: "'Discussion of precise time and frequency measurement'" <[email protected]> Sent: Monday, April 21, 2008 8:40 PM Subject: [time-nuts] Power supply for Thunderbolt
> I'm in the process of buying a Thunderbolt, and will need to provide > it with > some volts. > > I sat down over the weekend to design a linear supply for it. > Initially > things looked OK using a 12-0-12 transformer, and a few IC voltage > regulators, but then I did some worst case design and dissipation > analysis, > and found that I needed to use a 15-0-15 transformer to allow for > a -10% > mains variation, and add pass transistors and lots of heat sinking > to all > the regulators to allow for a +10% mains variation. > > Add to that transformer regulation issues (over-size transformer), > the time > to design the PCB and the cost of getting it made, and things > started to > look expensive :-(. > > I can probably source a linear supply on eBay, but these are > typically > pretty large and heavy. For example: eBay item number 330201077319 > > So is it reasonable to use an SMPS, and add additional filtering to > the > output? Typically these talk in terms on 150mV ripple & noise which > I need > to reduce by a factor of ten or better. > > If you have been there, done that, I'd be interested to hear what > you did. > > Thanks > Dave Partridge > ----- Original Message ----- From: "David C. Partridge" <[EMAIL PROTECTED]> To: "'Discussion of precise time and frequency measurement'" <[email protected]> Sent: Monday, April 21, 2008 8:40 PM Subject: [time-nuts] Power supply for Thunderbolt > I'm in the process of buying a Thunderbolt, and will need to provide > it with > some volts. > > I sat down over the weekend to design a linear supply for it. > Initially > things looked OK using a 12-0-12 transformer, and a few IC voltage > regulators, but then I did some worst case design and dissipation > analysis, > and found that I needed to use a 15-0-15 transformer to allow for > a -10% > mains variation, and add pass transistors and lots of heat sinking > to all > the regulators to allow for a +10% mains variation. > > Add to that transformer regulation issues (over-size transformer), > the time > to design the PCB and the cost of getting it made, and things > started to > look expensive :-(. > > I can probably source a linear supply on eBay, but these are > typically > pretty large and heavy. For example: eBay item number 330201077319 > > So is it reasonable to use an SMPS, and add additional filtering to > the > output? Typically these talk in terms on 150mV ripple & noise which > I need > to reduce by a factor of ten or better. > > If you have been there, done that, I'd be interested to hear what > you did. > > Thanks > Dave Partridge Hi David- that Meanwell unit looks a good choice. For the record, I measured the following current requirements for an OEM Tbolt using a 428B. Measured Thunderbolt DC supply rail loadings - Initial loads-within 10 -20 sec from power applied. +12 730 mA +5 ~400 mA -12 not checked After 2 minutes- +12 200 mA (sudden drop from ~700 mA, just prior to 2 mins) +5 300 mA -12 not checked After 3 hours- +12 150 mA +5 300 mA -12 ~ 2 mA Tbolt mon running (i.e. serial port activity) in latter two cases-not for initial load test Regards DaveB, NZ _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
