On Fri, 17 Mar 2023 08:21:23 -0700, John Larkin <jlarkin@highlandSNIPMEtechnology.com> wrote:> >I've been asked to design an 8-channel dummy load board. It's not very >challenging but somebody's got to do it. It will be used to simulate >small loads like solenoids or relays or torque motors. It needs some >inductance too, because the drivers often PWM. Maybe 10 or so watts >per channel. > >I could do this electronically, but it would a lot easier and more >rugged if I use wirewound resistors. I was thinking of making a >conductance DAC, namely resistors R 2R 4R etc switched in parallel >across the inputs with an SSR per resistor. > >But there is a history of clever load banks. When I was an EE student >at Tulane, two semisters of Electrical Machinery (with lab) was >mandatory. It was a pain but I learned a lot. We had a big load bank >in the machinery lab, a string of giant series resistors with a >3-position knife switch at each node. That made me think about using >series-parallel combinations to hit some target value. > >https://www.dropbox.com/s/x3e7xxi13n6wd1o/Load_Banks_1.jpg?raw=1 > >The upper pic is the ancient Tulane load bank as I remember it. > >I was thinking about the lower circuit for my gadget. I could use >wirewould resistors and kink the leads to space them maybe 3/4 inch >above my PCB, in the air stream. The higher value resistors might be >2512 surface mounts. > >I think there is a tool to bend and kink resistor leads. Or we could >send a bunch out to a service maybe. > > >Active I=kV with a delay would give you an inductance. Does the driver really care? Where'd the word 'dummy' originate in the spec? If it reflects the attitude of the buyer, I'd say 'No Bid'. I've had it with idiots like that. RL
load bank puzzle
Started by ●March 17, 2023
Reply by ●March 17, 20232023-03-17
Reply by ●March 17, 20232023-03-17
On Fri, 17 Mar 2023 17:14:59 -0400, legg <legg@nospam.magma.ca> wrote:>On Fri, 17 Mar 2023 08:21:23 -0700, John Larkin ><jlarkin@highlandSNIPMEtechnology.com> wrote: > >> >>I've been asked to design an 8-channel dummy load board. It's not very >>challenging but somebody's got to do it. It will be used to simulate >>small loads like solenoids or relays or torque motors. It needs some >>inductance too, because the drivers often PWM. Maybe 10 or so watts >>per channel. >> >>I could do this electronically, but it would a lot easier and more >>rugged if I use wirewound resistors. I was thinking of making a >>conductance DAC, namely resistors R 2R 4R etc switched in parallel >>across the inputs with an SSR per resistor. >> >>But there is a history of clever load banks. When I was an EE student >>at Tulane, two semisters of Electrical Machinery (with lab) was >>mandatory. It was a pain but I learned a lot. We had a big load bank >>in the machinery lab, a string of giant series resistors with a >>3-position knife switch at each node. That made me think about using >>series-parallel combinations to hit some target value. >> >>https://www.dropbox.com/s/x3e7xxi13n6wd1o/Load_Banks_1.jpg?raw=1 >> >>The upper pic is the ancient Tulane load bank as I remember it. >> >>I was thinking about the lower circuit for my gadget. I could use >>wirewould resistors and kink the leads to space them maybe 3/4 inch >>above my PCB, in the air stream. The higher value resistors might be >>2512 surface mounts. >> >>I think there is a tool to bend and kink resistor leads. Or we could >>send a bunch out to a service maybe. >> >> >> > >Active I=kV with a delay would give you an inductance.A real inductor stores energy, which a synthesized inductor usually doesn't. Stored energy pumps current into flyback diodes or equivalent.> >Does the driver really care?It certainly might.> >Where'd the word 'dummy' originate in the spec? If it reflects >the attitude of the buyer, I'd say 'No Bid'. I've had it with >idiots like that.Oh, they are just a biggish aerospace company. No bid? Is that a good business model?> >RLhttps://en.wikipedia.org/wiki/Dummy_load
Reply by ●March 17, 20232023-03-17
fredag den 17. marts 2023 kl. 22.13.01 UTC+1 skrev legg:> On Fri, 17 Mar 2023 08:21:23 -0700, John Larkin > <jla...@highlandSNIPMEtechnology.com> wrote: > > > > >I've been asked to design an 8-channel dummy load board. It's not very > >challenging but somebody's got to do it. It will be used to simulate > >small loads like solenoids or relays or torque motors. It needs some > >inductance too, because the drivers often PWM. Maybe 10 or so watts > >per channel. > > > >I could do this electronically, but it would a lot easier and more > >rugged if I use wirewound resistors. I was thinking of making a > >conductance DAC, namely resistors R 2R 4R etc switched in parallel > >across the inputs with an SSR per resistor. > > > >But there is a history of clever load banks. When I was an EE student > >at Tulane, two semisters of Electrical Machinery (with lab) was > >mandatory. It was a pain but I learned a lot. We had a big load bank > >in the machinery lab, a string of giant series resistors with a > >3-position knife switch at each node. That made me think about using > >series-parallel combinations to hit some target value. > > > >https://www.dropbox.com/s/x3e7xxi13n6wd1o/Load_Banks_1.jpg?raw=1 > > > >The upper pic is the ancient Tulane load bank as I remember it. > > > >I was thinking about the lower circuit for my gadget. I could use > >wirewould resistors and kink the leads to space them maybe 3/4 inch > >above my PCB, in the air stream. The higher value resistors might be > >2512 surface mounts. > > > >I think there is a tool to bend and kink resistor leads. Or we could > >send a bunch out to a service maybe. > > > > > > > Active I=kV with a delay would give you an inductance.sure it can slow the current rise like an inductor but it won't keep the current flowing after turnoff
Reply by ●March 17, 20232023-03-17
On Friday, 17 March 2023 at 16:40:16 UTC, Jan Panteltje wrote:> On a sunny day (Fri, 17 Mar 2023 08:21:23 -0700) it happened John Larkin > <jla...@highlandSNIPMEtechnology.com> wrote in > <u6091ide59fffa8ga...@4ax.com>: > > > >I've been asked to design an 8-channel dummy load board. It's not very > >challenging but somebody's got to do it. It will be used to simulate > >small loads like solenoids or relays or torque motors. It needs some > >inductance too, because the drivers often PWM. Maybe 10 or so watts > >per channel. > > > >I could do this electronically, but it would a lot easier and more > >rugged if I use wirewound resistors. I was thinking of making a > >conductance DAC, namely resistors R 2R 4R etc switched in parallel > >across the inputs with an SSR per resistor. > Yes why not.. > 'SSR' == solid state rectifier ? you mean relay? You get AC as input right? > oh wait you mean sold state relay.... > googling SSR gives among many things Wikipedia with "Soviet Socialist Republic" > >But there is a history of clever load banks. When I was an EE student > >at Tulane, two semisters of Electrical Machinery (with lab) was > >mandatory. It was a pain but I learned a lot. We had a big load bank > >in the machinery lab, a string of giant series resistors with a > >3-position knife switch at each node. That made me think about using > >series-parallel combinations to hit some target value. > > > >https://www.dropbox.com/s/x3e7xxi13n6wd1o/Load_Banks_1.jpg?raw=1 > We use rectangles as resistor symbol here :-) > >The upper pic is the ancient Tulane load bank as I remember it. > > > >I was thinking about the lower circuit for my gadget. I could use > >wirewould resistors and kink the leads to space them maybe 3/4 inch > >above my PCB, in the air stream. The higher value resistors might be > >2512 surface mounts. > > > >I think there is a tool to bend and kink resistor leads. Or we could > >send a bunch out to a service maybe. > My setup: > https://panteltje.nl/pub/power_resistors_IMG_6291.JPG > uses test leads with alligator clips to switch configuration.clever idea using the user's arse as a power monitor.
Reply by ●March 17, 20232023-03-17
On Friday, 17 March 2023 at 21:42:04 UTC, John Larkin wrote:> No bid? Is that a good business model?sometimes it is.
Reply by ●March 17, 20232023-03-17
On 3/17/2023 11:40 AM, Jan Panteltje wrote:> On a sunny day (Fri, 17 Mar 2023 08:21:23 -0700) it happened John Larkin > <jlarkin@highlandSNIPMEtechnology.com> wrote in > <u6091ide59fffa8gafp93ipmmejp424r5j@4ax.com>: > >> >> I've been asked to design an 8-channel dummy load board. It's not very >> challenging but somebody's got to do it. It will be used to simulate >> small loads like solenoids or relays or torque motors. It needs some >> inductance too, because the drivers often PWM. Maybe 10 or so watts >> per channel. >> >> I could do this electronically, but it would a lot easier and more >> rugged if I use wirewound resistors. I was thinking of making a >> conductance DAC, namely resistors R 2R 4R etc switched in parallel >> across the inputs with an SSR per resistor. > > Yes why not.. > 'SSR' == solid state rectifier ? you mean relay? You get AC as input right? > oh wait you mean sold state relay.... > googling SSR gives among many things Wikipedia with "Soviet Socialist Republic" > > >> But there is a history of clever load banks. When I was an EE student >> at Tulane, two semisters of Electrical Machinery (with lab) was >> mandatory. It was a pain but I learned a lot. We had a big load bank >> in the machinery lab, a string of giant series resistors with a >> 3-position knife switch at each node. That made me think about using >> series-parallel combinations to hit some target value. >> >> https://www.dropbox.com/s/x3e7xxi13n6wd1o/Load_Banks_1.jpg?raw=1 > > We use rectangles as resistor symbol here :-) > > > >> The upper pic is the ancient Tulane load bank as I remember it. >> >> I was thinking about the lower circuit for my gadget. I could use >> wirewould resistors and kink the leads to space them maybe 3/4 inch >> above my PCB, in the air stream. The higher value resistors might be >> 2512 surface mounts. >> >> I think there is a tool to bend and kink resistor leads. Or we could >> send a bunch out to a service maybe. > > My setup: > https://panteltje.nl/pub/power_resistors_IMG_6291.JPG > uses test leads with alligator clips to switch configuration. > > So as to Soviet Socialist Republic > Here a very funny thing happened in politics > We just had elections, and a new party, BBB (translated: farmers people movement) > wiped out all parties going from zero to more than the biggest ones. > Protest against all the CO2 idiots who want to close farms because cows make CO2. > I voted for them too :-) > We need farmers and their produce. > We will see where it goes now... > > >I thought cows made methane which is a worse greenhouse gas than CO2. -- Dogs make me happy. Humans make my head hurt.
Reply by ●March 17, 20232023-03-17
On Saturday, March 18, 2023 at 3:33:04 AM UTC+11, Clive Arthur wrote:> On 17/03/2023 15:21, John Larkin wrote: > > > > I've been asked to design an 8-channel dummy load board. It's not very > > challenging but somebody's got to do it. It will be used to simulate > > small loads like solenoids or relays or torque motors. It needs some > > inductance too, because the drivers often PWM. Maybe 10 or so watts > > per channel. > <snip> > > Plenty of power rheostats available. eBay has loads, many new. > Inductance is a separate matter (though they will have some of course - > get tubular rheostats and bung a ferrite rod down the centre?).Not good idea. Rheostats get hot. and ferrite rods tend to have a low Curie temperature. Manganese-zinc ferrites have Curie temperatures from 120°C – 300°C. -- Bill Sloman, Sydney
Reply by ●March 18, 20232023-03-18
On 18-Mar-23 8:14 am, legg wrote:> Where'd the word 'dummy' originate in the spec? If it reflects > the attitude of the buyer, I'd say 'No Bid'. I've had it with > idiots like that."Dummy load" seems a terminology common enough not to suggest anything about the buyer. Sylvia.
Reply by ●March 18, 20232023-03-18
On a sunny day (Fri, 17 Mar 2023 21:36:10 -0500) it happened John S <Sophi.2@invalid.org> wrote in <tv3831$20nan$1@dont-email.me>:>On 3/17/2023 11:40 AM, Jan Panteltje wrote: >> So as to Soviet Socialist Republic >> Here a very funny thing happened in politics >> We just had elections, and a new party, BBB (translated: farmers people movement) >> wiped out all parties going from zero to more than the biggest ones. >> Protest against all the CO2 idiots who want to close farms because cows make CO2. >> I voted for them too :-) >> We need farmers and their produce. >> We will see where it goes now... >> >> >> > >I thought cows made methane which is a worse greenhouse gas than CO2.Yea, those CO2 or climate fear mongering idiots are against everything https://pubmed.ncbi.nlm.nih.gov/8675759/>Dogs make me happy. Humans make my head hurt.We should kill all dogs? those make CO2 too. and dogs shit everywhere. It is all about selling snake oil. What needs to happen is build more nuclear power plants so we can create our own environment to keep inhabiting our locations. Heating, aircos, shelters.. But the brainless a-technical paranoid greta thunberg clueless crowd is the advertising agent for climate crap sellers. Climate change is caused by earth orbit variations: http://old.world-mysteries.com/alignments/mpl_al3b.htm
Reply by ●March 18, 20232023-03-18
On a sunny day (Fri, 17 Mar 2023 10:22:33 -0700) it happened John Larkin <jlarkin@highlandSNIPMEtechnology.com> wrote in <5l791i1hev1qsuei98p7t83mprc4881jhk@4ax.com>:>On Fri, 17 Mar 2023 16:40:09 GMT, Jan Panteltje <alien@comet.invalid> >wrote: > >>On a sunny day (Fri, 17 Mar 2023 08:21:23 -0700) it happened John Larkin >><jlarkin@highlandSNIPMEtechnology.com> wrote in >><u6091ide59fffa8gafp93ipmmejp424r5j@4ax.com>: >> >>> >>>I've been asked to design an 8-channel dummy load board. It's not very >>>challenging but somebody's got to do it. It will be used to simulate >>>small loads like solenoids or relays or torque motors. It needs some >>>inductance too, because the drivers often PWM. Maybe 10 or so watts >>>per channel. >>> >>>I could do this electronically, but it would a lot easier and more >>>rugged if I use wirewound resistors. I was thinking of making a >>>conductance DAC, namely resistors R 2R 4R etc switched in parallel >>>across the inputs with an SSR per resistor. >> >>Yes why not.. >>'SSR' == solid state rectifier ? you mean relay? You get AC as input right? >>oh wait you mean sold state relay.... > >Yes. > >>googling SSR gives among many things Wikipedia with "Soviet Socialist Republic" >> >> >>>But there is a history of clever load banks. When I was an EE student >>>at Tulane, two semisters of Electrical Machinery (with lab) was >>>mandatory. It was a pain but I learned a lot. We had a big load bank >>>in the machinery lab, a string of giant series resistors with a >>>3-position knife switch at each node. That made me think about using >>>series-parallel combinations to hit some target value. >>> >>>https://www.dropbox.com/s/x3e7xxi13n6wd1o/Load_Banks_1.jpg?raw=1 >> >>We use rectangles as resistor symbol here :-) > >Quaint olde world customs. > >> >> >> >>>The upper pic is the ancient Tulane load bank as I remember it. >>> >>>I was thinking about the lower circuit for my gadget. I could use >>>wirewould resistors and kink the leads to space them maybe 3/4 inch >>>above my PCB, in the air stream. The higher value resistors might be >>>2512 surface mounts. >>> >>>I think there is a tool to bend and kink resistor leads. Or we could >>>send a bunch out to a service maybe. >> >>My setup: >> https://panteltje.nl/pub/power_resistors_IMG_6291.JPG >> uses test leads with alligator clips to switch configuration. > >We have a couple of Kikusui benchtop electronic load boxes, which are >handy. They can do square wave loads, handy for checking power supply >dynamics. > >I want programmable 0 to 1 zillon ohms, isolated, ac/dc, 10 or 20 >watts, metered, overload protected, 8 loads per board, maybe 4 square >inches per channel. > >I was wondering if anyone had cute ideas. I considered PWM-ing a big >resistor, but that has complications. > >> >>So as to Soviet Socialist Republic >>Here a very funny thing happened in politics >>We just had elections, and a new party, BBB (translated: farmers people movement) >>wiped out all parties going from zero to more than the biggest ones. >>Protest against all the CO2 idiots who want to close farms because cows make CO2. >>I voted for them too :-) >>We need farmers and their produce. > >Most people think eating is good. > >>We will see where it goes now... >> >> > >People will surely get tired of crazy prices and blackouts and food >shortages and waiting hours to recharge their cars.I did a switched inductor thing many many years ago, it was for tuning and used relays IIRC (up to a few hundred kHz). I see electronics to simulate inductors as a possibility. But what sort of users need this? Normally you would test on the real thing any unexpected things could exist in a real system, parasitic capacitances, lead resistance and inductances, unexpected couplings.. what not. Nothing like a real test. Bridge rectifier with a power MOSFET in it for AC load? Gives all sort of problems too...
