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.
load bank puzzle
Started by ●March 17, 2023
Reply by ●March 17, 20232023-03-17
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?). -- Cheers Clive
Reply by ●March 17, 20232023-03-17
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=1We 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...
Reply by ●March 17, 20232023-03-17
On Fri, 17 Mar 2023 16:32:56 +0000, Clive Arthur <clive@nowaytoday.co.uk> 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?).We want 8 channels on a PC board, programmable resistance.
Reply by ●March 17, 20232023-03-17
On Friday, March 17, 2023 at 8:21:37 AM UTC-7, 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 ...So far, a Variac and big resistor on the output is a possibility. Or, a few paint cans full of oil, with rotary switch and immersed lower-watt resistors (Cantenna style), could work. But, 'load' for even just a battery test can be anything from 1 ohm to hundreds, just for the batteries in my household; the only easy way to make the load you want, is to specify it first, then build one. That means the 'load board' is a connector plenum, and the loads would be plugins to that, plucked from a bucket of prebuilt options. Eight-channel is easy: design one, build eight, and strap 'em together.
Reply by ●March 17, 20232023-03-17
fredag den 17. marts 2023 kl. 17.58.53 UTC+1 skrev John Larkin:> On Fri, 17 Mar 2023 16:32:56 +0000, Clive Arthur > <cl...@nowaytoday.co.uk> 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?). > We want 8 channels on a PC board, programmable resistance.8*10W is going to require quite a bit of cooling https://www.pickeringtest.com/en-dk/product/load-resistor-module-40r-to-295r-011 ;)
Reply by ●March 17, 20232023-03-17
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.
Reply by ●March 17, 20232023-03-17
On Fri, 17 Mar 2023 10:17:30 -0700 (PDT), Lasse Langwadt Christensen <langwadt@fonz.dk> wrote:>fredag den 17. marts 2023 kl. 17.58.53 UTC+1 skrev John Larkin: >> On Fri, 17 Mar 2023 16:32:56 +0000, Clive Arthur >> <cl...@nowaytoday.co.uk> 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?). >> We want 8 channels on a PC board, programmable resistance. > >8*10W is going to require quite a bit of cooling > >https://www.pickeringtest.com/en-dk/product/load-resistor-module-40r-to-295r-011 ;)I was thinking of kink-leading some axial wirewound resisors like they do. We'll have a lot of air flow so the cooling should be OK. Wirewound resistors can get very hot.
Reply by ●March 17, 20232023-03-17
On Fri, 17 Mar 2023 10:07:32 -0700 (PDT), whit3rd <whit3rd@gmail.com> wrote:>On Friday, March 17, 2023 at 8:21:37?AM UTC-7, 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 ... > >So far, a Variac and big resistor on the output is a possibility.Not on a PC board. Variacs are AC devices anyhow. Big and expensive.>Or, a few paint cans full of oil, with rotary switch and immersed lower-watt >resistors (Cantenna style), could work. > >But, 'load' for even just a battery test can be anything from 1 ohm to hundreds, >just for the batteries in my household; the only easy way to make the load >you want, is to specify it first, then build one. That means the 'load board' is >a connector plenum, and the loads would be plugins to that, plucked from >a bucket of prebuilt options. > >Eight-channel is easy: design one, build eight, and strap 'em together.This will be a product, a plugin board to a rackmount instrument.
Reply by ●March 17, 20232023-03-17
John Larkin <jlarkin@highlandSNIPMEtechnology.com> Wrote in message:r> I've been asked to design an 8-channel dummy load board. It's not verychallenging but somebody's got to do it. It will be used to simulatesmall loads like solenoids or relays or torque motors. It needs someinductance too, because the drivers often PWM. Maybe 10 or so wattsper channel.I could do this electronically, but it would a lot easier and morerugged if I use wirewound resistors. I was thinking of making aconductance DAC, namely resistors R 2R 4R etc switched in parallelacross the inputs with an SSR per resistor. But there is a history of clever load banks. When I was an EE studentat Tulane, two semisters of Electrical Machinery (with lab) wasmandatory. It was a pain but I learned a lot. We had a big load bankin the machinery lab, a string of giant series resistors with a3-position knife switch at each node. That made me think about usingseries-parallel combinations to hit some target value.https://www.dropbox.com/s/x3e7xxi13n6wd1o/Load_Banks_1.jpg?raw=1The upper pic is the ancient Tulane load bank as I remember it.I was thinking about the lower circuit for my gadget. I could usewirewould resistors and kink the leads to space them maybe 3/4 inchabove my PCB, in the air stream. The higher value resistors might be2512 surface mounts.I think there is a tool to bend and kink resistor leads. Or we couldsend a bunch out to a service maybe.Board assembly houses should have the lead crimpers. I believe it only works with tape reel packaging. Could be wrong but check with the vendor. Cheers -- ----Android NewsGroup Reader---- https://piaohong.s3-us-west-2.amazonaws.com/usenet/index.html
