- earbud / headphone wire - 1 Update
- Help please with PWM sewing machine pedal - 4 Updates
- Fuses, Am I That Stupid ? - 1 Update
- can bad cap = hot motor? - 1 Update
| Adrian Caspersz <email@here.invalid>: Aug 22 10:53AM +0100 On 18/08/2020 23:17, malua mada! wrote: > Suggest search terms...? > Thanks > Fritz It's got a name almost similar to your name ;-) Look for Litz headphone wire -- Adrian C |
| etpm@whidbey.com: Aug 21 11:34AM -0700 I have an old Singer sewing machine. It is a model 221, AKA a Featherweight. I got the thing at a garage sale for 5 or 10 bucks and everything was there but the foot pedal motor control. So I bought a modern PWM style control instead of an old carbon disc style one because it was supposed to be better. At least I think the new one is PWM. It is very light and doesn't get hot after lots of use. I think it may be under performing though because the little machine seems to run too slow. I did go through the machine, cleaning and adjusting it. It was dirty inside, had old congealed lubricants clogging and sticking stuff up. Things were also really out of adjustment so it would not have been able to sew even if it was turning freely. The machine now turns quite freely. It is oiled with the proper oil and the motor, which I also cleaned and lubricated, is lubricated with the proper grease. So after all that the machine still runs too slowly. At least in my opinion. The motor just doesn't seem to have much oomph and I'm wondering if maybe the foot pedal control is not delivering enough current and/or voltage. Since the control is PWM output would an analog meter like my Simpson 260 be a good tool to measure the current and voltage? Or maybe someone here knows already about these machines and the foot controls and can tell me what to expect from a properly operating control. And the best way to check it. Thanks, Eric --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus |
| "pfjw@aol.com" <peterwieck33@gmail.com>: Aug 21 12:36PM -0700 Ummmm ..... PWM controls are for DC motors for the most part. When used on AC motors, they will cut speed by some amount just by being in place. Motors are funny things. They draw rated current even when throttled, which is why VFDs are preferred for AC motors. Not so much the control heating up as the motor heating up if fed with a PWM device. https://www.amazon.com/Sew-link-Featherweight-Control-Pedal-PFW-196131/dp/B07DMSSF2R/ref=asc_df_B07DMSSF2R/?tag=hyprod-20&linkCode=df0&hvadid=241925305119&hvpos=&hvnetw=g&hvrand=4629272318479936685&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9007234&hvtargid=pla-466961777480&psc=1 Yes. There are some featherweight motors that are both AC or DC - but it will run better on AC. Peter Wieck Melrose Park, PA |
| Pimpom <nobody@nowhere.com>: Aug 22 02:38AM +0530 > --- > This email has been checked for viruses by Avast antivirus software. > https://www.avast.com/antivirus I've seen designs - but not the actual product - of cheap motor controls that can provide only half the power at full throttle. This is because the phase-controlled device is an SCR without any pre-rectification and conduct for only half of each AC cycle.. Maybe you have one of those. |
| Phil Allison <pallison49@gmail.com>: Aug 21 08:27PM -0700 Pimpom wrote: ------------ > controls that can provide only half the power at full throttle. > This is because the phase-controlled device is an SCR without any > pre-rectification and conduct for only half of each AC cycle.. ** SCR speed controls for AC/DC motors are brilliant things - cos they allow for back EMF feedback as well as very low speeds. The feedback keeps the speed steady with varying loads - while trigger speed controls built into drills use triacs and give no such benefit. The sewing machine foot controller is likely a triac type - which is a form of PWM too. ..... Phil |
| Michael_A_Terrell <terrell.michael.a@gmail.com>: Aug 21 04:10PM -0400 >> without opening. >> -- > We all know the Belfuse fuses were chemical fuses except for just *one* group contributor who is *never* wrong and said they aren't chemical fuses... What he doesn't know would fill entire libraries. I'll bet that he's never heard of a Klystrode, either. They replaced Klystrons in high power TV transmitters, but they wer more efficient so the station's power bill was lower. the 5MW UHF site that I maintaining had a $45,000 per month electric bill. It would have been about 15 to 20% lower if it used Klystrodes. -- Never piss off an Engineer! They don't get mad. They don't get even. They go for over unity! ;-) |
| "pfjw@aol.com" <peterwieck33@gmail.com>: Aug 21 10:27AM -0700 > I know modern caps are much better than old caps. However, why do you > suppose it is that motor run caps are so big for their voltage and > capacitance ratings compared to other non-polarized caps? I'm serious. That is not a bad question at all: a) Because they are AC-rated caps. b) Because the nature of a motor starting puts a tremendous load on the cap for a very short time, so they must be robust enough to absorb that shock, repeatedly and reliably, in addition to the actual voltage involved. So, whereas the actual operating voltage may be say.... 240 VAC, the start-cap must be rated (at a minimum) of 150% of the operating voltage. c) Typical NP caps are used a great deal in audio applications, where the voltages are small, and the frequencies high. d) Motor Run caps start around 370V, or so, are typically of much lower capacitance than a start-cap (and whereas replacement voltage may be higher, replacement capacitance should remain very close or identical to OEM). Hope that helps. Peter Wieck Melrose Park, PA |
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