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 > Your search for posts made by 'LScamper' found 42 matches.

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RE: Astable 555 Timer (Recommended Resistors Are NUTS!)

Can not get there without more stuff with a 555 timer as others have said. If you want to use a 555 make sure it is a cmos version, they can use much higher value resistors in the timing circuit. Still can not do it with just a 555. Arduino is a very good choice for doing almost anything you can think of. If you get China knock off it is very cheap. The software is free open source. You can find a program on the WEB to do almost anything you want and down load it for free. Programming it yourself is easy if you know some basic programming, if not it will take some learning! It is worth learning. Another option might be this or something like it. http://smile.amazon.com/Intermatic-TN311-Heavy-Grounded-Timer/dp/B005MMSTNG/ref=sr_1_6?ie=UTF8&qid=1417482365&sr=8-6&keywords=timer+3+times
LScamper 12/01/14 06:20pm Tech Issues
RE: Where did you get your Electrical knowledge?

Started as hobby at around 12 years old. Nike Hercules missile radar, computer fire control operator. Side note. Nike computer was analog with servos turning big gears that turned large potentiometers. Potentiometers were wound with sin and cos tapers that did the calculations to steer a missile to a target. Repaired TV and stereo equipment while in school. Spent 35 years working in fusion energy research on multi megajoule pulse power systems. Mostly did control and instrumentation for one of a kind very large physics experiments. Part of a team that designed, built, installed and maintained 2.5 gigawatt feedback amplifier chain to stabilize a plasma for a fusion experiment (filament power 500 kW). Three years working on Star Wars particle beam accelerator RF feedback control system. Helped design high speed x ray camera for National Ignition Facility. About 100 pS resolution time. Retired 2004 and now playing with taking pictures of water drops using an Arduino micro for timing control. Some of the pictures are in my sig.
LScamper 11/22/14 02:20pm Tech Issues
RE: LED flicker

A few terms. http://en.wikipedia.org/wiki/Ripple_%28electrical%29 Ripple is a periodic variation of DC at a the fundamental or multiple of the fundamental. In a full wave rectifier it is 120Hz. In a switcher it could be 10kHz to maybe 1MHz. http://www.tvss.net/trans/trans-x.htm Transient voltages are random and often caused be switching inductive loads. A capacitor of the correct value and type placed in the correct place will help to eliminate both ripple and transient voltages. LED flicker may be caused by a random fluctuating voltage, bad connection, bad LED, bad convertor, or other things that are slowly fluctuating. Ripple on a LED at 120Hz can not be seen with your eyes even though the light is varying. A slow fluctuating voltage may not be filtered out with a capacitor depending on the amount of current drawn and the length of time between fluctuations. The battery is a good filter at low frequencies, not so much at high frequencies. Putting the LED across the battery with the power on may tell you that the converter is bad ( a volt meter may help also). It may tell you that the LED flickers with the higher voltage at the battery from the converter. If it does not flicker then wiring to the filtered output of the converter may fix the problem. Anyway it is just another test to help narrow down the problem.
LScamper 11/20/14 10:29pm Tech Issues
RE: LED flicker

Unlikely that it will stop the flicker. Try the LED connected directly to the battery and see if it works there. The battery acts as a very large capacitor so there should be little ripple there.
LScamper 11/20/14 10:07am Tech Issues
RE: LED flicker

Schematic for Parallax 6300. http://12078.net/rv-stuff/Parallax_6300_Schematic.PDF You are correct in that there is a relay that connects the battery to the unfiltered loads, that is mostly lights, when power is off. When power is on the converter supplies about 5A to charge the battery and about 45A for other things. The problem comes when the power is on. The voltage regulator uses an SCR (40A, 200V on schematic) in a form of pulse width modulation to charge the battery. For higher charge rates the SCR conducts for a long time, maybe many cycles. As the battery charges the SCR conducts less time as called for by the voltage comparator (SCR T106A1 on schematic). The T106A1 turns on when the battery voltage reaches the regulator set point and keeps the 40 A SCR from turning back on. The 40A SCR relies on the CURRENT in it going to about ZERO to turn off. This happens when the full wave rectified DC from the four diodes goes to zero at the zero crossing 120 times per second. If you put a capacitor on the output of the diodes the voltage will NOT go to ZERO. If it does not go to zero the SCR will not shut off and the battery will try to charge to the sine wave peak value, around 18V! This may not be exactly how it works but very close. I know this will happen because I installed a fan with speed control one time in parallel with a light in the ceiling. The lights got really bright and measured 18V. I had to get out my scope to find out what was happening. I rewired the fan to the filtered output and all was well.
LScamper 11/19/14 07:19pm Tech Issues
RE: LED flicker

CAUTION!!!!! Do not put any capacitor anywhere on the unfiltered converter output line (Blue wire on converter). That is the output that most likely is driving the lights. The capacitor can be connected to the filtered battery output lead (Red battery lead on the converter).
LScamper 11/19/14 05:30pm Tech Issues
RE: Drilling P.C. Boards (tips solicited)

More tips! Soldering station I have. Not a Weller but seems to work fine. Would not use in industrial setting. http://smile.amazon.com/X-TRONIC-6040-Soldering-SOLDERING-MAGNIFYING/dp/B0052M8SZA/ref=sr_1_1?ie=UTF8&qid=1416156860&sr=8-1&keywords=x-tronic+6000&pebp=1416156864766 They have models without the hot air. Radioshack has some of the best solder I have ever used. http://www.radioshack.com/high-tech-rosin-core-silver-bearing-solder-1-5-oz-/6400013.html http://www.radioshack.com/rosin-core-solder-2-5-oz-/6400005.html Radioshack desolding braid is also about the best I have used. http://www.radioshack.com/desoldering-braid/6402090.html And for seeing small things on a circuit board you can not go without this. http://www.amazon.com/Donegan-Optical-Binocular-Magnifier-Lensplate/dp/B000YZCSBU/ref=sr_1_2?ie=UTF8&qid=1416155615&sr=8-2&keywords=optivisor+lensplate+%237 The #7 lens plate works for me but there are others to look at. Then this light works perfect with the magnifier. http://www.amazon.com/Led-Light-Attachment-For-Optivisor/dp/B0058ECQ46/ref=sr_1_3?ie=UTF8&qid=1416155227&sr=8-3&keywords=optivisor
LScamper 11/16/14 09:53am Tech Issues
RE: Drilling P.C. Boards (tips solicited)

For small hand held hole enlarging the Dremel bit set that Gdetrailer points to is fine. The carbide bits used for mass PC board drilling are much sharper but are brittle and may break if not careful. If you are coating the boards remember that will make it very hard to repair! If using wire wrap don't try to make it neat. Short straight routing, called rats nest, is best to keep cross talk down.
LScamper 11/15/14 09:32am Tech Issues
RE: Drilling P.C. Boards (tips solicited)

Don't need any fancy stuff to enlarge perf board holes unless you have many to do. Try a search for pin vise. Something like this. Not saying this one is good. http://www.amazon.com/Empire-Level-2715-Precision-Drill/dp/B001DZE5BQ/ref=sr_1_4?ie=UTF8&qid=1416009599&sr=8-4&keywords=pin+vise I have used a pin vise and small bits to enlarge hundreds if not thousands of holes in perf board in the last 40 years.
LScamper 11/14/14 05:03pm Tech Issues
RE: Unknown Brand AC/DC Inductive Ammeter?

This is a review of the meter. Clicky
LScamper 11/09/14 10:05am Tech Issues
RE: Cannot connect to public WiFi

Had the same problem with a new Dell Windows 8.1 desktop out of the box. Would connect but no internet access. Called Dell, after many things to try no luck. It was new and nothing had been installed. They said try to do refresh to new condition using windows recovery. After doing that it worked perfectly and I never had a problem with it again. All so have an HP laptop. I could not get some programs to run sometimes on it. Tried for several weeks. Gave up and did a refresh to new condition. Never had a problem with it after that. Strange that two new Windows 8.1 computers had bad Windows installed from factory. Just luck I guess, but strange. Both have been working perfectly for months now.
LScamper 11/07/14 10:22am Technology Corner
RE: Paralleling Power Supply Units Made Easy ???

Yet another stability paper. About the same as the one Salvo noted. It shows how to measure stability in a CLOSED LOOP system. You do not have to open the loop. It injects a stimulus into the loop. Is this the same as injecting a stimulus as in connecting another power supply in parallel? I think so. As long as the stimulus is not so big that it causes the loop to saturate it seems it should work. http://www.edn.com/design/power-management/4412230/Testing-a-power-supply---Stability--Part-three-
LScamper 11/04/14 12:12am Tech Issues
RE: Paralleling Power Supply Units Made Easy ???

From this EDN note "Multiple PSUs share load" Using diodes to isolate power supplies. http://www.edn.com/design/power-management/4419835/Multiple-PSUs-share-load The results were disappointing, since they show that in the case of ±1% voltage deviation, 90% of the power is supplied by a single supply. Basically, this circuit is not a good solution for power supplies with more than a few tens of millivolts difference. The problem is that not all off-the-shelf power supplies have output voltage adjustments – especially not the sealed ones. To solve this issue, a circuit was developed to ensure load sharing using off-the-shelf power supplies and components (Figure 2).
LScamper 10/27/14 10:26am Tech Issues
RE: Paralleling Power Supply Units Made Easy ???

Salvo wrote: “That's not quite right. The supply that sees higher voltage than it's setpoint will just shut off. The pwm duty cycle will go to zero percent. This is a very safe condition for the supply.” Correct, this is one of the condition that I think could happen. “When the first supply reaches its setpoint it goes into constant voltage mode. When the other supply charges the battery voltage above that set point the first supply's control loop tries to lower the voltage to its setpoint, it can not do that. It will keep trying and will saturate. At that point the first supply is operating open loop. Depending on the supply design it may just shut the output off, a good thing.” Condition 2: “It is possible that the error amp, being over driven, will saturate and reverse its output if it is not designed well. This would turn on the output to full voltage, a bad thing!” Salvo wrote: “ You're not going to overstress the error amp either. The amp is probably powered by 12V. The reference voltage to the error amp is usually around 5V. If the first supply is at 15V then the second supply needs to go up to 15V * 12/5 = 36V. That's highly unlikely that the two setpoints are that far apart.” It has been many years and my memory is not what it use to be! My terminology may be wrong when I said error amp is over driven. What I am trying to say is that at the point that the control loop, while trying to lower the output voltage, will at some point saturate. At this point I agree with what you say. “The pwm duty cycle will go to zero percent.” At this point the control loop is now open loop. When it is open loop there is no feedback to drive the + and – inputs to the error amp to the same voltage. A long time ago operational amplifiers had a nasty habit of reversing or latching their outputs in the opposite direction than it should when this happened. This would turn the converter output full on, a bad thing. Maybe this condition can no longer happen, I don't know. With parts being made in China I would not bet on anything. From MEXICOWANDERER's last post it seems as if something bad happens when paralleled! Maybe what I just said?
LScamper 10/19/14 05:29pm Tech Issues
RE: Paralleling Power Supply Units Made Easy ???

Some thoughts: Salvo wrote: “Having designed many dc/dc converters, I see this stability issue way over blown. If the ps has a phase margin of 45 degrees, then guaranteed, there's no stability issues. 30 to 45 degrees of phase margin is standard design practice.” X2. I see no problems with paralleling two supplies under some conditions. While they are both in constant current there should be no problem. If there is diode isolation between them there should be no problem. I do see a problem if there is no diode isolation and one supply reaches its voltage set point and the other is still charging the battery. When the first supply reaches its set point it goes into constant voltage mode. When the other supply charges the voltage above that set point the first supply's control loop tries to lower the voltage to its set point, it can not do that. It will keep trying and will saturate. At that point the first supply is operating open loop. Depending on the supply design it may just shut the output off, a good thing. It is possible that the error amp, being over driven, will saturate and reverse its output if it is not designed well. This would turn on the output to full voltage, a bad thing! I can only guess that these cheap supplies are not designed worrying to much about all the possible ways they will be used. I don't think anyone can say exactly how they will react to being paralleled without a complete knowledge of how they are designed.
LScamper 10/19/14 01:16pm Tech Issues
RE: Buck Your Solar with a Mex Gizmo?

Just a few thoughts (or lack there of). It will be interesting to see what happens when you drive a buck converter with a constant current source (gizmo between panel and controller). I think that the panel voltage and converter output current will go into wild oscillations at the point that the load (battery) is asking for more power than the panel can provide. “I can use some resistance between the panel and the gizmo to reduce its input voltage to less than 32v.” When the gizmo is not asking for any current there will not be any voltage drop across the resistance and the full open circuit panel voltage will be at the gizmo input! Some have suggested using a power supply to drive a solar controller. This woud be interesting also, driving a controller that is made for a current source input with a voltage source input. If it is a MPPT controller will it try to find the maximum power point. That is will it lower the input resistance trying to find the maximum power until it burns itself out? Just wondering.
LScamper 10/13/14 09:00pm Tech Issues
RE: LCD Backlit DC Voltmeter (doesn't require power)

RoyB wrote: "I DO NOT want to go with the SHUNT TYPE current taps as then I have to deal with high current 'HOT' DC wiring running back to my meter console." Put a 2K resistor on each of the shunt meter leads at the shunt. Then run the meter to the other side of the 2K resistors. The resistors will not change the meter reading and will limit any short circuit current to a harmless value.
LScamper 09/19/14 09:03am Tech Issues
RE: solar fuses

Reprint from 4/10/2014 RE: Proper Fusing Of Three Parallel Panels Trying to make sense of panel fusing. A fuse is a current protection device. A fuse at the output of a panel is to protect the wires from the fuse to whatever it is connected to, mainly the controller. An array is the parallel connection of two or more panels (strings). A string is the series connection of two or more cells. A panel can be say 30 cells or 90 cells. A string can be one panel of say 90 cells or three panels of 30 cells in series, same exact thing! Say a panel is rated at 10A short circuit current and the fuses are 15A. So what happens if there is a short directly at a panel before the fuse? If there is only one panel the panel output goes to zero and the controller gets no input. The fuse will not blow, no current through it. If there are two panels in parallel and one shorts directly at a panel the output the voltage goes to zero and the controller gets no input. The short circuit current supplied by the other panel, 10A, now goes through both fuses, the one on the good panel and the one on the shorted panel. Neither fuse blows because they are rated to handle the current from one panel. The wires are safe because they are rated to handle at least the short circuit current from one panel. If there are three panels in parallel and one shorts directly at a panel the output voltage goes to zero and the controller gets no input. The short circuit current supplied by the other two panels is added, now 20A total, and flows through each of the good panel’s fuses, 10A each, and through the shorted panel fuse. This fuse now gets two times its normal current, 20A, and should blow from over current. When the fuse blows the voltage goes up at the controller and will still charge the battery from the two good panels. If the wire is rated to handle the current from the two good panels no fuse would be required. This would be the case in most of the installations talked about on the forum; most use much larger wire than needed to keep voltage drop at a minimum. This brings us to a reason not to use fuses at the panel, voltage drop! In order for a fuse to blow it has to dissipate some power to heat it to the melting point. This means that the fuse must have resistance. A 7A fuse resistance is about .013 Ohms and a 10A fuse resistance is about .008 Ohms. A 10-gauge wire has a resistance of about .001 Ohm per foot. So adding a 7A fuse is like adding about 13 feet of 10-gauge wire from the panel and a 10A fuse is like adding about 8 feet of 10-gauge wire. Plus there are all the connections that add resistance and could become loose or not a make good connection. Bottom line is if the wires from each panel can handle the total current from all the panels, most likely they can, there is no reason to use fuses and they introduce voltage drop plus added connections.
LScamper 09/18/14 09:01am Tech Issues
RE: eTopxizu (cheapowatt) 30 amp power supply Guinea Pig

Edit my last post, not enough coffee! "As you increase the output the inductor stays on longer and the voltage across it increases." Should be: As you increase the output the inductor stays on longer and the CURRENT increases.
LScamper 09/15/14 09:54am Tech Issues
RE: eTopxizu (cheapowatt) 30 amp power supply Guinea Pig

OK first things first. The D13009K that you ordered is not an FET, it is a transistor! I don't know what the actual part that gave up is, I have not tried to look it up. You can not just replace a transistor with an FET!!! The drive circuit is much different. Second, the buzzing most likely is an inductor saturating. As you increase the output the inductor stays on longer and the voltage across it increases. At some point it will saturate. When that happens the current will spike in the output transistors or FET which ever is used. When the current spikes the power dissipation (heat) increases rapidly as you have seen. Next is the rating of the transistors that you ordered, 12A. With two in parallel as it looks to be that would only be good for 24 Amps. Surprised they survived at 30 A, but still not sure what the actual parts in the supply are.
LScamper 09/15/14 09:14am Tech Issues
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