On 07/22/2016 06:33 PM, John Larkin wrote:> On Fri, 22 Jul 2016 17:21:21 -0400, Phil Hobbs > <pcdhSpamMeSenseless@electrooptical.net> wrote: > >> On 07/22/2016 05:07 PM, ChesterW wrote: >>> On 7/22/16 1:22 AM, Phil Hobbs wrote: <snip> >>>> >>>> Same guy who said "never use a phototransistor for anything". ;) >>> >>> I know. At first I wondered if you had been kidnapped and were trying >>> to embed secret messages for help. I'm glad you're OK. >>> >>> If a lot of phototransistors were all in a pile, it might make a >>> good paperweight. Maybe pour over with clear epoxy? >> >> Personally I'd probably burn them for winter warmth. ;) >> >>> >>>> >>>> But the OP's application seems to be very low speed, so a barefoot >>>> phototransistor plus heavy bypassing should work fine. A 100-ms >>>> time constant gets rid of a lot of nasties. >>>> >>> >>> Hmmmm, maybe. Even running 110V for instrument power through trays >>> with motor power is chancy, much less small signals. >> >> Yeah, VFDs are seriously bad neighbours. You can get millivolts of crud >> across solid metal frames that are probably down in the microohms. >> Circulating current of some amperes, with millivolt drops, is what make >> ground loops so seemingly mysterious. Jiggling a wire changes the >> contact resistance and effectively makes or breaks the ground loop. >> Nickel-plated connectors make this much worse, because they form >> Ni-NiO-Ni tunnel junctions. >> > > This is the VFD for a vent fan on the roof. It was making 20 volt > spikes on the other side of the building. It was a nuisance to filter. > > https://dl.dropboxusercontent.com/u/53724080/Circuits/Filters/Filter.JPGI remember seeing that earlier this year. Between that and Sutro, you folks can probably draw sparks between your fingertips if you stand just right. ;) Cheers Phil "Living in a fairly benign EMI environment" 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
Phototransistor fed to a transimpedance amplifier
Started by ●July 17, 2016
Reply by ●July 22, 20162016-07-22
Reply by ●July 23, 20162016-07-23
On 7/22/16 4:21 PM, Phil Hobbs wrote:> On 07/22/2016 05:07 PM, ChesterW wrote: >> On 7/22/16 1:22 AM, Phil Hobbs wrote: <snip> >>> >>> Same guy who said "never use a phototransistor for anything". ;) >> >> I know. At first I wondered if you had been kidnapped and were trying >> to embed secret messages for help. I'm glad you're OK. >> >> If a lot of phototransistors were all in a pile, it might make a >> good paperweight. Maybe pour over with clear epoxy? > > Personally I'd probably burn them for winter warmth. ;) > >> >>> >>> But the OP's application seems to be very low speed, so a barefoot >>> phototransistor plus heavy bypassing should work fine. A 100-ms >>> time constant gets rid of a lot of nasties. >>> >> >> Hmmmm, maybe. Even running 110V for instrument power through trays >> with motor power is chancy, much less small signals. > > Yeah, VFDs are seriously bad neighbours. You can get millivolts of crud > across solid metal frames that are probably down in the microohms. > Circulating current of some amperes, with millivolt drops, is what make > ground loops so seemingly mysterious. Jiggling a wire changes the > contact resistance and effectively makes or breaks the ground loop. > Nickel-plated connectors make this much worse, because they form > Ni-NiO-Ni tunnel junctions. > >> I got a paid trip to the Aleutians once because a PE broke that >> rule. > > Did you get to visit Spruce Island? I hope to do that one day. I've > only been as far as Homer. Terrific place in the summer. > >> >> Hey OP, u some place interesting? U use cable, I come fix. > > It's supposed to be 114 in Riyadh tomorrow. ;) > > Cheers > > Phil Hobbs >First stop on the trip was Homer. Agree it's a great little town. There was an ultrasonic level sensor at the head of a new wastewater treatment plant, controlling a couple of pumps with VFDs. Of course a very glamorous assignment :). The PE had run the instrument power with the motor power and this caused the sensor electronics to reset every 20 seconds or so. They had to control it by hand 24/7. It was part of the contractors check-off list, and they wanted to make sure it was really fixed, so I got to spend a few day wandering around Homer. The fish restaurants on the spit really spoil you. Commercial fishing is big in Alaska, and the Fish and Game guys cut off the season after the boats reach a certain catch limit. They weigh the fish when the boats off-load. This leaves a lot of capacity still at sea after cut-off, so they don't get much precision in their control. So after Homer, I got to go out to Dutch Harbor to judge the feasibility of weighing the catch right on board the boats. I didn't get a chance to go to Kodiak. The area is certainly lovely, but what is the draw of Spruce Island? -- Best Regards, ChesterW +++ Dr Chester Wildey Founder MRRA Inc. Electronic and Optoelectronic Instruments MRI Motion, fNIRS Brain Scanners, Counterfeit and Covert Marker Detection Fort Worth, Texas, USA www.mrrainc.com wildey at mrrainc dot com
Reply by ●July 23, 20162016-07-23
On 7/22/16 5:33 PM, John Larkin wrote:> On Fri, 22 Jul 2016 17:21:21 -0400, Phil Hobbs > <pcdhSpamMeSenseless@electrooptical.net> wrote: > >> On 07/22/2016 05:07 PM, ChesterW wrote: >>> On 7/22/16 1:22 AM, Phil Hobbs wrote: <snip> >>>> >>>> Same guy who said "never use a phototransistor for anything". ;) >>> >>> I know. At first I wondered if you had been kidnapped and were trying >>> to embed secret messages for help. I'm glad you're OK. >>> >>> If a lot of phototransistors were all in a pile, it might make a >>> good paperweight. Maybe pour over with clear epoxy? >> >> Personally I'd probably burn them for winter warmth. ;) >> >>> >>>> >>>> But the OP's application seems to be very low speed, so a barefoot >>>> phototransistor plus heavy bypassing should work fine. A 100-ms >>>> time constant gets rid of a lot of nasties. >>>> >>> >>> Hmmmm, maybe. Even running 110V for instrument power through trays >>> with motor power is chancy, much less small signals. >> >> Yeah, VFDs are seriously bad neighbours. You can get millivolts of crud >> across solid metal frames that are probably down in the microohms. >> Circulating current of some amperes, with millivolt drops, is what make >> ground loops so seemingly mysterious. Jiggling a wire changes the >> contact resistance and effectively makes or breaks the ground loop. >> Nickel-plated connectors make this much worse, because they form >> Ni-NiO-Ni tunnel junctions. >> > > This is the VFD for a vent fan on the roof. It was making 20 volt > spikes on the other side of the building. It was a nuisance to filter. > > https://dl.dropboxusercontent.com/u/53724080/Circuits/Filters/Filter.JPG > > > >The inductors on the outside look really cool. I'm doing that on my next design! :) -- Best Regards, ChesterW
Reply by ●July 23, 20162016-07-23
>I didn't get a chance to go to Kodiak. The area is certainly lovely, but >what is the draw of Spruce Island?It's where St. Herman of Alaska lived. He was a monk from Valaam in north-western Russia who with his brothers walked all the way across Siberia and crossed the sea to bring the Gospel to the indigenous people of what was then Russian Alaska. They all died there. Herman spent his life in service to them, often opposing the Russian authorities on their behalf. Really a remarkably holy place--there are pilgrimages there all the time. Maybe next year. Cheers Phil Hobbs
Reply by ●July 24, 20162016-07-24
John Larkin wrote:> On Fri, 22 Jul 2016 17:21:21 -0400, Phil Hobbs > <pcdhSpamMeSenseless@electrooptical.net> wrote: > >> On 07/22/2016 05:07 PM, ChesterW wrote: >>> On 7/22/16 1:22 AM, Phil Hobbs wrote:<snip> >>>> >>>> Same guy who said "never use a phototransistor for anything". ;) >>> >>> I know. At first I wondered if you had been kidnapped and were trying >>> to embed secret messages for help. I'm glad you're OK. >>> >>> If a lot of phototransistors were all in a pile, it might make a >>> good paperweight. Maybe pour over with clear epoxy? >> >> Personally I'd probably burn them for winter warmth. ;) >> >>> >>>> >>>> But the OP's application seems to be very low speed, so a barefoot >>>> phototransistor plus heavy bypassing should work fine. A 100-ms >>>> time constant gets rid of a lot of nasties. >>>> >>> >>> Hmmmm, maybe. Even running 110V for instrument power through trays >>> with motor power is chancy, much less small signals. >> >> Yeah, VFDs are seriously bad neighbours. You can get millivolts of crud >> across solid metal frames that are probably down in the microohms. >> Circulating current of some amperes, with millivolt drops, is what make >> ground loops so seemingly mysterious. Jiggling a wire changes the >> contact resistance and effectively makes or breaks the ground loop. >> Nickel-plated connectors make this much worse, because they form >> Ni-NiO-Ni tunnel junctions. >> > > This is the VFD for a vent fan on the roof. It was making 20 volt > spikes on the other side of the building. It was a nuisance to filter. > > https://dl.dropboxusercontent.com/u/53724080/Circuits/Filters/Filter.JPG > > > >Did you try adding a 4th toroid as a tri-filar common mode filter? BTW, did the red and blue toroids get close to saturation on power peaks? That increases their loss and tends to (at minimum) shift the spike phase for an even lower interference.
Reply by ●July 24, 20162016-07-24
On 7/23/16 6:51 PM, Phil Hobbs wrote:>> I didn't get a chance to go to Kodiak. The area is certainly lovely, but >> what is the draw of Spruce Island? > > It's where St. Herman of Alaska lived. He was a monk from Valaam in north-western Russia who with his brothers walked all the way across Siberia and crossed the sea to bring the Gospel to the indigenous people of what was then Russian Alaska. They all died there. Herman spent his life in service to them, often opposing the Russian authorities on their behalf. > > Really a remarkably holy place--there are pilgrimages there all the time. Maybe next year. > > Cheers > > Phil Hobbs >It's a harsh country even today. I can only imagine what it was like in Herman's time. -- Best Regards, ChesterW
