Some reading for a lazy Sunday afternoon. A typical femto-second laser might give 65kW 0.1ps light pulses at a rate of 80MHz. But some applications can't handle a powerful light pulse every 12.5ns, for example fluorescence-lifetime measurements (we don't want to re-excite any molecules before achieving 100% decay). The solution is to add a light modulator, and run it from a pulse-picker. The picker should have adjustable pulse width and delay or phase, to exactly enable the modulator in the middle of a selected pulse. Pulse picker synchronizers typically cost $6000, but I figured it shouldn't be hard to design and make them for say, under $100. Here's my recently-completed RIS-761 divide-by-N pulse picker. https://www.dropbox.com/sh/ofzc5xo880ne8ag/AACSmMZdooCPf57UT950R37ea?dl=0 It combines fast logic gates with a few analog-circuit functions to provide synchronization and shaping. In practice the phase and width settings would only be made once per laser setup, so knobs are not provided. The delay / phase is adjustable over a 20ns range, more than needed, and the width from 5 to 18ns. The 99cm pcb slides into a Hammond 2x4x4-inch extruded box, which is the most expensive component. Parson my poor cell-phone photo quality. -- Thanks, - Win
cotton-pickin Pulse Picker
Started by ●June 5, 2016
Reply by ●June 5, 20162016-06-05
On 06/05/2016 03:31 PM, Winfield Hill wrote:> Some reading for a lazy Sunday afternoon. > > A typical femto-second laser might give 65kW 0.1ps light pulses at a rate of > 80MHz. But some applications can't handle a powerful light pulse every 12.5ns, > for example fluorescence-lifetime measurements (we don't want to re-excite any > molecules before achieving 100% decay). The solution is to add a light > modulator, and run it from a pulse-picker. The picker should have adjustable > pulse width and delay or phase, to exactly enable the modulator in the middle of > a selected pulse. Pulse picker synchronizers typically cost $6000, but I > figured it shouldn't be hard to design and make them for say, under $100. > > Here's my recently-completed RIS-761 divide-by-N pulse picker. > https://www.dropbox.com/sh/ofzc5xo880ne8ag/AACSmMZdooCPf57UT950R37ea?dl=0 > > It combines fast logic gates with a few analog-circuit functions to provide > synchronization and shaping. In practice the phase and width settings would > only be made once per laser setup, so knobs are not provided. The delay / phase > is adjustable over a 20ns range, more than needed, and the width from 5 to 18ns. > The 99cm pcb slides into a Hammond 2x4x4-inch extruded box, which is the most > expensive component. Parson my poor cell-phone photo quality. > >Looks fun. I gather you're mounting those BNCs on both sides of the board. I'm way too chicken to use SMT BNCs, because grad students are always stepping on BNC cables and tearing them out of the plug. These are the ones I like--they're solid zinc alloy and pass the stomp test with no worries: http://tinyurl.com/jlbazso Of course it's a bit tough to mount them right opposite each other. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
Reply by ●June 5, 20162016-06-05
On Sun, 5 Jun 2016 15:46:30 -0400, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:>On 06/05/2016 03:31 PM, Winfield Hill wrote: >> Some reading for a lazy Sunday afternoon. >> >> A typical femto-second laser might give 65kW 0.1ps light pulses at a rate of >> 80MHz. But some applications can't handle a powerful light pulse every 12.5ns, >> for example fluorescence-lifetime measurements (we don't want to re-excite any >> molecules before achieving 100% decay). The solution is to add a light >> modulator, and run it from a pulse-picker. The picker should have adjustable >> pulse width and delay or phase, to exactly enable the modulator in the middle of >> a selected pulse. Pulse picker synchronizers typically cost $6000, but I >> figured it shouldn't be hard to design and make them for say, under $100. >> >> Here's my recently-completed RIS-761 divide-by-N pulse picker. >> https://www.dropbox.com/sh/ofzc5xo880ne8ag/AACSmMZdooCPf57UT950R37ea?dl=0 >> >> It combines fast logic gates with a few analog-circuit functions to provide >> synchronization and shaping. In practice the phase and width settings would >> only be made once per laser setup, so knobs are not provided. The delay / phase >> is adjustable over a 20ns range, more than needed, and the width from 5 to 18ns. >> The 99cm pcb slides into a Hammond 2x4x4-inch extruded box, which is the most >> expensive component. Parson my poor cell-phone photo quality. >> >> >Looks fun. I gather you're mounting those BNCs on both sides of the >board. I'm way too chicken to use SMT BNCs, because grad students are >always stepping on BNC cables and tearing them out of the plug. > >These are the ones I like--they're solid zinc alloy and pass the stomp >test with no worries: > >http://tinyurl.com/jlbazso > >Of course it's a bit tough to mount them right opposite each other. > >Cheers > >Phil HobbsWe use the Bomar V-BITE connectors on some of our boxes. http://www.mouser.com/images/bomarinterconnect/lrg/LargeBomar361V509E_504ER.jpg They are sort of edge-launch, with the connector centerline almost in the PCB plane. They really grab onto the board. -- John Larkin Highland Technology, Inc lunatic fringe electronics
Reply by ●June 5, 20162016-06-05
Phil Hobbs wrote...> > Looks fun. I gather you're mounting those BNCs on both sides of the > board. I'm way too chicken to use SMT BNCs, because grad students > are always stepping on BNC cables and tearing them out of the plug. > > These are the ones I like--they're solid zinc alloy and pass the > stomp test with no worries: http://tinyurl.com/jlbazsoYes, I've long used those beasts, but have become a recent fan of stacked-pair BNCs. Interestingly, all manufacturers use 0.6-inch vertical spacing, but other than that, they differ substantially. I'm using the molex 73415-3980, which uses strong metal brackets and features a pair of 2-56 threaded panel-securing mount holes. http://www.molex.com/molex/products/datasheet.jsp?part=active/0734153980_RF_COAX_CONNECTORS.xml -- Thanks, - Win
Reply by ●June 5, 20162016-06-05
On 06/05/2016 04:07 PM, John Larkin wrote:> On Sun, 5 Jun 2016 15:46:30 -0400, Phil Hobbs > <pcdhSpamMeSenseless@electrooptical.net> wrote: > >> On 06/05/2016 03:31 PM, Winfield Hill wrote: >>> Some reading for a lazy Sunday afternoon. >>> >>> A typical femto-second laser might give 65kW 0.1ps light pulses >>> at a rate of 80MHz. But some applications can't handle a >>> powerful light pulse every 12.5ns, for example >>> fluorescence-lifetime measurements (we don't want to re-excite >>> any molecules before achieving 100% decay). The solution is to >>> add a light modulator, and run it from a pulse-picker. The >>> picker should have adjustable pulse width and delay or phase, to >>> exactly enable the modulator in the middle of a selected pulse. >>> Pulse picker synchronizers typically cost $6000, but I figured >>> it shouldn't be hard to design and make them for say, under >>> $100. >>> >>> Here's my recently-completed RIS-761 divide-by-N pulse picker. >>> https://www.dropbox.com/sh/ofzc5xo880ne8ag/AACSmMZdooCPf57UT950R37ea?dl=0 >>> >>> >>> >>> >>>It combines fast logic gates with a few analog-circuit functions to provide>>> synchronization and shaping. In practice the phase and width >>> settings would only be made once per laser setup, so knobs are >>> not provided. The delay / phase is adjustable over a 20ns range, >>> more than needed, and the width from 5 to 18ns. The 99cm pcb >>> slides into a Hammond 2x4x4-inch extruded box, which is the most >>> expensive component. Parson my poor cell-phone photo quality. >>> >>> >> Looks fun. I gather you're mounting those BNCs on both sides of >> the board. I'm way too chicken to use SMT BNCs, because grad >> students are always stepping on BNC cables and tearing them out of >> the plug. >> >> These are the ones I like--they're solid zinc alloy and pass the >> stomp test with no worries: >> >> http://tinyurl.com/jlbazso >> >> Of course it's a bit tough to mount them right opposite each >> other. >> >> Cheers >> >> Phil Hobbs > > We use the Bomar V-BITE connectors on some of our boxes. > > http://www.mouser.com/images/bomarinterconnect/lrg/LargeBomar361V509E_504ER.jpg > > > >They are sort of edge-launch, with the connector centerline almost> in the PCB plane. They really grab onto the board.I looked at those, but iirc they're getting hard to find, and I don't really trust the mounting pins on the back--they're actually a loop of wire press-fit into a slot in the connector body. Plus they're only supported by the board. Something with a nice bulkhead thread that transfers the stress to the box instead of the solder joints is very reassuring. (You do have to let the board move around a bit.) Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
Reply by ●June 5, 20162016-06-05
Phil Hobbs wrote...> > Something with a nice bulkhead thread that transfers the > stress to the box instead of the solder joints is very > reassuring. (You do have to let the board move around a bit.)As I mentioned, the ones I'm using have such a feature, and the wire is soldered. BTW, I added a pic of the pcb, panel and connectors from the back to the dropbox folder. -- Thanks, - Win
Reply by ●June 5, 20162016-06-05
John Larkin wrote...> > Phil Hobbs wrote: >> Winfield Hill wrote: >>> Some reading for a lazy Sunday afternoon. >>> >>> A typical femto-second laser ... >>> Here's my recently-completed RIS-761 divide-by-N pulse picker. >>> https://www.dropbox.com/sh/ofzc5xo880ne8ag/AACSmMZdooCPf57UT950R37ea?dl=0 >>> >>> It combines fast logic gates with a few analog-circuits ...BTW, John, note my use of 65LVDS2-series LVDS receivers throughout, instead of comparators, inspired by your post a few years ago. They're great! Fast, stable, in sot-23 package. I added a Bourns CD143A-SR3.3 TVS (in a sot-23-sized package) to protect their fragile inputs. -- Thanks, - Win
Reply by ●June 5, 20162016-06-05
On 5 Jun 2016 14:12:24 -0700, Winfield Hill <hill@rowland.harvard.edu> wrote:>John Larkin wrote... >> >> Phil Hobbs wrote: >>> Winfield Hill wrote: >>>> Some reading for a lazy Sunday afternoon. >>>> >>>> A typical femto-second laser ... >>>> Here's my recently-completed RIS-761 divide-by-N pulse picker. >>>> https://www.dropbox.com/sh/ofzc5xo880ne8ag/AACSmMZdooCPf57UT950R37ea?dl=0 >>>> >>>> It combines fast logic gates with a few analog-circuits ... > > BTW, John, note my use of 65LVDS2-series LVDS receivers > throughout, instead of comparators, inspired by your > post a few years ago. They're great! Fast, stable, in > sot-23 package. I added a Bourns CD143A-SR3.3 TVS (in > a sot-23-sized package) to protect their fragile inputs.I have some data on offset voltage and jitter vs cm voltage... somewhere. They are pretty amazing fast CMOS-input rrio comparators, not advertised as such. Their outputs are pretty fierce, too. About 1/4 the price of an official comparator at this speed. I've used them as customer-input triggers and they don't seem to get damaged. A parallel RC in series with the input will protect the esd diodes from gross DC overloads. You might save a few ns by using the NC7SV74K8X flip-flop. Tpd is 1 ns, faster than old ECL. 16 cents! We've done a few custom pulse picker boards, usually with a bunch of other functions, like photodiode amps, multiple delay/width outputs, other i/o. Here's one, really a laser controller, but its basic function is pulse picking. https://dl.dropboxusercontent.com/u/53724080/PCBs/T940_first_board.jpg -- John Larkin Highland Technology, Inc lunatic fringe electronics
Reply by ●June 6, 20162016-06-06
On Sunday, June 5, 2016 at 4:51:23 PM UTC-4, Winfield Hill wrote:> Phil Hobbs wrote... > > > > Something with a nice bulkhead thread that transfers the > > stress to the box instead of the solder joints is very > > reassuring. (You do have to let the board move around a bit.) > > As I mentioned, the ones I'm using have such a feature, > and the wire is soldered. BTW, I added a pic of the pcb, > panel and connectors from the back to the dropbox folder.Oh, what are those BNC "header" type things? Are they custom? George H. (Thanks for the schematic.)> > > -- > Thanks, > - Win
Reply by ●June 6, 20162016-06-06
George Herold wrote...> Winfield Hill wrote: >> Phil Hobbs wrote... >>> >>> Something with a nice bulkhead thread that transfers the >>> stress to the box instead of the solder joints is very >>> reassuring. (You do have to let the board move around a bit.) >> >> As I mentioned, the ones I'm using have such a feature, >> and the wire is soldered. BTW, I added a pic of the pcb, >> panel and connectors from the back to the dropbox folder. > > Oh, what are those BNC "header" type things? > Are they custom?Were you asking me? My parts were Molex 73415-3980, http://www.molex.com/molex/products/datasheet.jsp?part=active/0734153980_RF_COAX_CONNECTORS.xml -- Thanks, - Win
