- Measuring audio amp output power - 6 Updates
- Solid State relay kills induction motor fans - 8 Updates
| "Ron D." <Ron.Dozier@gmail.com>: Jul 30 09:32PM -0700 Audio load: http://www.mcmelectronics.com/product/28-048 (No mention of tolerance) Done. Scopes have a lot of errors. A DVM may work, but pay attention to frequency response. If you stick to a sine wave you won't need a TRMS meter. Next problem, you need to know the resistor value accurately. I don't think you want or need want 0.001% accuracy. |
| Phil Allison <pallison49@gmail.com>: Jul 31 02:14AM -0700 Ron D. wrote: > Audio load: http://www.mcmelectronics.com/product/28-048 > (No mention of tolerance) ** I use the same resistors for all amplifier bench testing. Submerged in water, they can handle 1000W each. Using a pair and a simple switching scheme gives 4, 8 and 16 ohms. > Scopes have a lot of errors. ** That's a a bit harsh. Many analogue scopes manage 2% accuracy for time and amplitude & modern DSOs have on-screen displays of the same parameters with better than 1% accuracy. > A DVM may work, but pay attention to frequency response. ** Most can be trusted to about 1kHz on sine waves. .... Phil |
| Trevor Wilson <trevor@SPAMBLOCKrageaudio.com.au>: Jul 31 08:17PM +1000 On 31/07/2015 2:32 PM, Ron D. wrote: > Scopes have a lot of errors. A DVM may work, but pay attention to > frequency response. If you stick to a sine wave you won't need a > TRMS meter. **Digital 'scopes often have true RMS display capability, with excellent accuracy. > Next problem, you need to know the resistor value accurately. > I don't think you want or need want 0.001% accuracy. **Far and away the biggest source of inaccuracy lies with line Voltage regulation. Or lack of it. I would certainly not panic about resistor accuracy nor 'scope accuracy, when faced with typical line Voltage swings. Naturally, most professionals use a variable auto transformer (aka: Variac™) and a line Voltage monitor. -- Trevor Wilson www.rageaudio.com.au --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus |
| "pfjw@aol.com" <pfjw@aol.com>: Jul 31 07:00AM -0700 On Monday, July 27, 2015 at 6:09:33 PM UTC-4, Ralph Mowery wrote: > You can probably go at least 5 and maybe 10 times the power on the load > resistor if you put it in some water or oil. Many times that if you have > liquid nitrogen. NO!!!! Most metallic conductors are Zero-Resistance at cryogenic temperatures. So, a wire-wound resistor may drop off to near-zero in liquid nitrogen. |
| "Ralph Mowery" <rmowery28146@earthlink.net>: Jul 31 11:05AM -0400 <pfjw@aol.com> wrote in message news:ab86ef38-7eac-4270-93f0-017fbea84a34@googlegroups.com... > NO!!!! > Most metallic conductors are Zero-Resistance at cryogenic temperatures. > So, a wire-wound resistor may drop off to near-zero in liquid nitrogen. The liquid nitrogen was mainly a joke to the extreme of cooling. However if enough power is being used, the resistor its self would be heated to a more normal temperture and would be way above the temperature of the nitrogen. This woudl bring the resistance back up. |
| MJC <gravity@mjcoon.plus.com>: Jul 31 04:42PM +0100 In article <ab86ef38-7eac-4270-93f0-017fbea84a34@googlegroups.com>, pfjw@aol.com says... > Most metallic conductors are Zero-Resistance at cryogenic temperatures. > So, a wire-wound resistor may drop off to near-zero in liquid nitrogen. If only superconductors for liquid N2 temperatures (77K, -196C) were so common! Even at liquid He (4.22K, -270C) only a minority of metals make the transition. My Kaye and Laby says: "At low temperatures the effects of impurities etc become increasingly important and these largely determine the value of the residual resistance to which many metals decrease at low temperature." Mike. |
| M Philbrook <jamie_ka1lpa@charter.net>: Jul 30 02:41PM -0400 In article <d821f37c-370c-4030-b5b9-557793c313bc@googlegroups.com>, pyroartist.dw@gmail.com says... > > > Dean > > Do you do TIG/MIG welding in this garage? > No. I don't own a TIG/MIG welder. You need a non inductive load on the same circuit, along with a capacitor across it.. Your motor windings are getting killed by the drop out of the TRIAC at each phase angle. You need to suppress it somehow so that both the HV pulse that shouldn't be there and lack of lower Z at the base of the sine wave, for the motor and cap of the motor to properly operate.. These are cheap motors and they run warm to start with, minimum copper and coating on the wire is used. Try getting your hands on a motor run capacitor, somewhere around 3..5uf at the proper rated voltage and put that across the load side of your SSR. ALso, putting a non-inductive load on the output helps, too... If you can get a low wattage incandescient bulb that would be fine or maybe a 5 watt R at around 400 ohms or so across the SSR load, along with the run cap. Also, I suspect when you connect these components, you'll also hear a slight difference of motor noise, which indicates this issue.. SSR switches don't always have a proper snubber in them, so you may also want to use a 100R and .1 Cap in series around the SSR, back to the soure so that the load will cycle back to the line on spikes. Have a good day Jamie |
| avagadro7@gmail.com: Jul 30 04:48PM -0700 diode the relay use the resistor use 2 Tyco/Bosch mechanical relays with diodes for relays and inputs |
| avagadro7@gmail.com: Jul 30 04:51PM -0700 On Wednesday, July 29, 2015 at 1:27:35 PM UTC-4, Pat wrote: > eventually open. Unfortunately, I can't think of any way to explain > why that would happen. > Pat the thermometer rapidly operates relay on and off circuitry passing something of this to the fans who are confused square one without dioding separating the systems unbalanced properties. |
| avagadro7@gmail.com: Jul 30 05:01PM -0700 AC relay with a triac-output optoisolator, with a smallish capacitor shunting > the input terminals (1 uF?), there ought to be no drive-side problems. /////////// they're mating http://goo.gl/Dj00S9 |
| David Lesher <wb8foz@panix.com>: Jul 31 02:55AM > The motor still spins easily. There is no DC continuity from the power p= >lug but I beleive this is normal for induction motors? Perhaps the overheat= > sensor has opened permenently. You got it. As they age the bearing dry and they pull more current. Eventually they open the Microtemp protecter within.... -- A host is a host from coast to coast.................wb8foz@nrk.com & no one will talk to a host that's close.......................... Unless the host (that isn't close).........................pob 1433 is busy, hung or dead....................................20915-1433 |
| Phil Allison <pallison49@gmail.com>: Jul 30 08:25PM -0700 David Lesher wrote: > > sensor has opened permenently. > You got it. As they age the bearing dry and they pull more current. > Eventually they open the Microtemp protecter within.... ** "The motor still spins easily" contradicts that idea. Seen a few cheap Chinese fans with tight/stuck bearings - takes a fair bit of solvent to get them spinning again. The OP has no so far bothered to open a fan a check the motor wiring for continuity. ... Phil |
| "Ron D." <Ron.Dozier@gmail.com>: Jul 30 09:42PM -0700 Deane: What relay are you using? What is the the motor? Some SSR bricks designed for this purpose have 3-32 V for an input and no series resistor is required. A heat sink with the appropriate thermal grease is. They have to be triac or back to back SCR's. Some offer to switch at zero current. It should be random. Some require series resistors. Some SSR's are triacs, dual SCR's, SCR's (won;t work) or MOSFETS (won;t work). |
| kenny.sourcing@gmail.com: Jul 30 10:55PM -0700 On Tuesday, July 28, 2015 at 10:06:47 AM UTC+8, Deane Williams wrote: > Does anyone know of a reason why I can't run an induction motor from a SS relay? What is killing the fans? I have taken two apart and there is no smoke smell, no visible damage and if there is a capacitor it tests OK. > Thanks for any ideas. I am going to switch over to a mechanical relay. > Dean If you need the thermal fuse, please feel free to contact xx.liu@setfuse.com. We are thermal fuse, MOV and thermal protected MOV manufacturer in China. Any question, please do not hesitate to inform us. Best Regards Leo |
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1 Response to Digest for sci.electronics.repair@googlegroups.com - 14 updates in 2 topics
Nice intro good explanation thanks for sharing.
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