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 > Your search for posts made by 'LScamper' found 56 matches.

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RE: 80VDC 10A fuse?

No need for a fuse as it will never blow. (Salvo X2) "Fuses are to protect the wire--not to protect devices so that is why I'd use a 30 amp fuse with #10 wire." X2. Small point to remember, the fuse should be located at the source. In this case at the panel to protect the wiring just as a fuse should be located at the battery if it is to protect the wiring.
LScamper 02/09/14 09:50am Tech Issues
RE: Helping

"If you can't fix it with a hammer, it's an electrical problem." ? I always fix old TVs with a hammer. Works most of the time.
LScamper 02/05/14 09:33am Tech Issues
RE: Big Project LED's

"do you have a engineering link, wiki's are NOT always correct" http://www.learnabout-electronics.org/ac_theory/ac_waves02.php http://arcarc.xmission.com/PDF_Electronics/Alternating%20Current%20-%20Part%202.pdf
LScamper 01/28/14 11:20am Tech Issues
RE: Big Project LED's

MEX heat sink http://www.allelectronics.com/make-a-store/item/HS-176/17.25-ALUMINUM-HEATSINK/1.html should be about .3 degree C / Watt in free air. So say max temp is going to be 65 degree C and ambient is 25 Degree that would be a 40 degree rise. So LED power could be 40/.3 = about 130W LED dissipation with that heat sink, more with fans. Not sure what the max temp rating of the LEDs are but this gives you an idea of what to expect. Also the LEDs will only conduct when the voltage is over their forward voltage drop rating. 33V x 4 = 132V. At that point they will draw a very high current spike. It will last long enough to smoke them. "Hoping the watts area under curve would be small enough for the devices to take it." It is the peak current that will kill the LEDs, not the average power. The peak current will last long enough during the peak of a half cycle that the LEDs think it is almost continuous power.
LScamper 01/25/14 05:03pm Tech Issues
RE: Big Project LED's

Gdetrailer wrote: "Half Wave rectification without filter caps will result in HALF the voltage at 89V in theory but in practice generally you can count on about half of the AC RMS or about 60V-70V. Assuming those LEDS are designed from 32V to 36 V or 96V-108V for three in series which should be well high enough." Not correct but not going into it. The LEDs will see the peak voltage of about 180V. At that time the current will be at maximum, well over what it is at 127V. The LEDs are sensitive to peak current and will smoke. Also, dissipating 400W will need a huge heat sink with fans on it. Or maybe water cooling.
LScamper 01/25/14 11:31am Tech Issues
RE: Big Project LED's

MEX wrote: "(4) 33 volt 100 watt LED's wired in series, with a 25 amp 800 PIV stud mounted rectifier for 127 vac operation. Dang I wish this would work, it would save me a lot of money. Or then it might make the prettiest smoke signal" Don't forget that the peak voltage is 1.4 times the RMS voltage. 127 x 1.4 = 178V! It will make a pretty smoke signal.
LScamper 01/25/14 10:09am Tech Issues
RE: Pure Sine Wave Inverter

I used a 1000W MSW inverter for years on several TVs, DVR, computer, and on my VIP211k sat receiver. It worked fine! Just bought a Samsung 32" TV. When I plugged it into my MSW there was a pretty loud buzz coming from inside the TV. It worked OK but I thought that the buzz was a sign of problems down the road. Better safe than sorry so I bought a 300W Go Power PSW inverter and it works fine, no more buzz! The buzz may be from an inductor in the switching power supply saturating because of the low peak voltage of the MSW inverter. Just guessing on that.
LScamper 01/16/14 06:40pm Technology Corner
RE: HELP AC Outlets blowing devices!

An open neutral between service panel bus bar and utility transformer would smoke things in the house as well as the RV. Problem should be between service panel bus bar and RV distribution panel. Start by loading as mex said but start at the house connector before plugging in the RV. Then work to the RV.
LScamper 01/06/14 09:56am Tech Issues
RE: HELP AC Outlets blowing devices!

MEXICOWANDERER has the best 100% sure way to find an open or high resistance nuetral. Do not plug in anything to the 50A plug until the problem is found. You will just destroy more equipment.
LScamper 01/05/14 09:46am Tech Issues
RE: Multi-meter recommendations, please!

Sorry for the overload! "I know a few people who have private museums of vintage test equipment" You must be talking about me. EICO Model 950B AC bridge, EICO Model 324 RF signal generator, EICO Model 425 5" Push Pull Oscilloscope, EICO Model 232 VTVM, battery eliminator with volt, current and a variac to set it and several other EICO items. Most bought by saving lunch money in 7th > 12th grade, late 50s early 60s. Still have the instruction manuals and the construction manual for them! Also have RCA Senior VoltOhmyst, Simpson Model 377, Triplett Model 666-R, and Triplett Model 310. A few other old meters laying around too. Have several Fluke meters some that I have used from the early 70s. Oh and one TEK RM 45 to heat the house! OK, back to this thread. If he is a true engineer he will appreciate quality equipment. You can'nt get better than Fluke! If he would like an oscilloscope, for about $400.00 on Amazon you can get a Rigol DS1102E 100MHz Digital Oscilloscope. It is a very good scope for little money for a scope. I have had one for about 3 years and really like it.
LScamper 12/21/13 07:05pm Technology Corner
RE: Mixing Batteries on Float-- Mex Test Update 2

A few observations about parallel batteries on float charge or just left connected in parallel. First assume that both batteries are in good shape and full charged. Mex said less than .1V after four or five days no problem. Seems like you could measure how one battery charges or discharges the other. Measure the current in the parallel connection between the two batteries. If they are at the same voltage there will be no current flowing from one to the other and the two batteries will not know they are connected together. If one is lower than the other you could measure the current and from that calculate the Amp hour discharge of the better battery. While in float charge if one battery has an open cell it will not draw any current from the charger and only the good battery will charge. If one battery has a shorted cell it will draw all or most of the current from the charger and may draw current from the good battery discharging it. I can’t think of any other interaction off the top of my head. Do you float charge or leave connected two six-volt batteries in series? If you do it seems that there is all most the same problem as two twelve-volt batteries in parallel. If left connected but not on a charger there is no problem. If one cell is open when float charging there will be no current and neither battery will charge. If one battery has a shorted cell all the good cells will over charge. Should you worry about either case? How often will a good battery go bad when it is left on a float charge or just left alone?
LScamper 12/20/13 10:41pm Tech Issues
RE: Induced power from nearby lines??

pianotuna thanks for the link. I found it fascinating.
LScamper 12/07/13 11:58am Tech Issues
RE: Converter In-Rush Thermistors etc, UPDATE -3

Salvo - like they say a picture is worth 1000 words! It would be nice, if you have time, to see the time delay from turn on to when the converter starts to supply load current. Is the thermistor at the lowest resistance at that time? Also would be interesting to see how fast the load current ramps up. Also would be interesting to see input current when applying load after the converter is powered up and the thermistor has had a chance to cool down. (A small load so it won’t destroy your converter!)
LScamper 12/06/13 01:21pm Tech Issues
RE: Induced power from nearby lines??

A little fun! Why are not these strays being used for good things or products? Maybe, for an emergency situation, you could buy a gadget you could charge your cell phone by unrolling a little wire under power lines. You could park your RV under power lines in the winter to heat it for free. If you live a cold area you could build your house using metal beams and let it heat it self. Maybe you could charge your RV battery by parking under power lines. The possibilities are almost limitless! OK how to measure it for those who know. Using a very high impedance voltmeter, RMS is best, measure the voltage from RV to ground. Then measure the current from the RV to ground with an ammeter. This will give you the Thevenin equivalent circuit. From this you can determine the maximum power transfer, the maximum power that you can use from this source. Will it be megawatts or microwatts? The curious want to know.
LScamper 12/05/13 11:41am Tech Issues
RE: Induced power from nearby lines??

Harvard is perfectly correct. This is a capacitive voltage divider. The capacitor between the power lines and the RV is small compared to the capacitor between the RV and ground. Thus a large voltage between the lines and the RV and a small voltage between the RV and ground. This would hold true even if the lines were DC instead of AC. The current drawn when you ground the RV would be small because the capacitance is small and the reactance is high. This was discussed a few times and I made the same case for a capacitive divider. But no one agreed with me, I don’t expect them to this time!
LScamper 12/04/13 09:15pm Tech Issues
RE: VARIAC....MEX?

Is the carbon sliding contact much different than the commutator brushes in a motor? They seem to last when the motor is turning fast under load.
LScamper 12/02/13 05:56pm Tech Issues
RE: Converter In-Rush Thermistors etc, UPDATE -3

ken white wrote: "The volt-second relationship is only valid for continuous current flow during steady state. If you exceed the kVA rating, with a large impulse current, then my guess is the core will saturate - it is being operated outside of design specifications... " First, I left out that core saturation is due to not enough magnetizing inductance that keeps the unloaded current down. It has nothing to do with load current. If you exceed the kVA rating with a large impulse current you may melt the windings but you will not saturate the core if you have enough V-S! I spent 35+ years in pulse-power. I have designed hundreds of high voltage pulse transformers. V-S is the king, VS=NBA. Current is not involved with core saturation.
LScamper 12/02/13 12:02pm Tech Issues
RE: Converter In-Rush Thermistors etc, UPDATE -3

ken white wrote: "Look at the B-H curves for the various magnetic materials and you will see the B field is controlled by the amp-turns which changes the permeability of the core and induced voltage. We are talking transient conditions and not steady state... Why do you think current has no effect?" B field is controlled by amp-turns --- This is true for DC. For transient and AC conditions the inductance, if designed correctly, keeps the current down and the core from saturating. It is the volt-seconds, that is the number of turns, the saturation flux of the magnetic material, and the size of the core, that determine if the core will saturate. V-S = NBA. Current is not involved.
LScamper 12/02/13 11:30am Tech Issues
RE: Converter In-Rush Thermistors etc, UPDATE -3

ken white wrote: "Not concerned about saturating the core of the transformer, or its kVA rating, when allowing 375 amps to flow? If saturated, the surge current will flow longer than 1/4 cycle and will persist for more cycles too... " ? How does high current saturate the core, volt - seconds stay the same?
LScamper 12/02/13 10:34am Tech Issues
RE: Converter In-Rush Thermistors etc, UPDATE -3

ktmrfs, sorry for not using your complete response. I agree with you but was trying to add something else to think about.
LScamper 11/30/13 11:40am Tech Issues
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