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Posts posted by bobleny

  1. So, I am working on an alarm system for my bike. As apart of that system, I would absolutely love to have it recognize me from a short distance, say 1 to 2 meters away, and deactivate the alarm and turn the accessories on. For that to work, I would obviously have to keep something on me that could either be read by the bike or something that could send a signal to the bike.

    My current thought is to use a micro controller to create a public private key pair. It would of course transmit the public key that the device I have on me will use to encrypt a secret password known only to device on me and the bike.

    How can I do something like this?
    Can anyone think of a way of doing this with out having to carry around a brick sized device? It would really be nice to just shove something in my wallet.
    Does anyone have any other ideas on how to something similar?


  2. So, I am looking at this project here:

    I am not actually interested in building an oscilloscope, I am more interested in building a 120-240 vac 50-60 hz signal analyzer. I would like to build something for monitoring the power being fed from the electric company into my house in as close to real time as I can get (obviously it takes time to convert and analyze the signal).

    The project won't work for what I want it to, but I feel that it is not too far off.

    My questions are...

    Can I increase it's voltage range to meet my needs, or do I need to use a transformer to lower my line voltage?
    --> If I use a transformer, is that going to significantly alter my signal?

    The probe circuitry uses an amplifier. Would I really need an amplifier in this case?

    He says he increased the sampling rate from the last project. Is there any way to actually calculate what that rate is?


  3. I don't see what all the fuss is about, you've got a range of appliances which either have built-in voltage regulators[...]

    Well, the fuss is, I don't want to break my electronics!! However, it never occurred to me that they would have a built in voltage regulator. Of course, now that you pointed that out, it seems stupid that they wouldn't. That's why it was so strange to me that there was such a large difference between what the devices input was rated for, and what the wall adapter was pumping out. Now I just feel stupid...


  4. No, an audio amplidier doesn't require a regulated power so adding one is a waste of time, just connect it to the battery via a fuse with roughly the same rating as the power supply.

    I was actually referring to a 15V regulator for everything.

    Did you measure the output voltages of the power supply with the load connected or disconnected? Some poor quality unregulated power supplies give a higher voltage unloaded than when loaded.

    I don't have an effective means of measuring the voltage under load. I doubt any of them are regulated, but the router, because of its 13.7v, might be.
    I'll just get a 12v regulator and run the modem, router, and answering machine off of that, and the speakers off of the battery.

    Or you could read the datasheet before you buy it. If it's a linear regulator, the output will be as specified until the input voltage drops below a certain level equal to the rated output voltage plus the drop out voltage.

    I did read the datasheet; that is where I learned of the dropout voltage. What I don't under stand is if it is a 12v fixed regulator with a 1.5v dropout, how can it have an input range of 5v to 25v? Does the voltage dropout when you give it a 12v input? I'm guessing the current drops, not the voltage, right? There are two graphs that mention the dropout voltage in the datasheet, which can be found in the link above or here: LT1085CT-12, but the graphs don't mean anything to me. They are comparing the input output differential to the output current, but I'm not really sure how that helps. That is where I got the idea of the max current dropping and not the voltage.

  5. So it's a diesel generator, not gasoline.

    I'm not sure if this is the right forum to put this in, I'm not even sure if this is the right site to post this in, but I have a diesel generator that produces 120V AC via a badly regulated alternator.

    From what I've read, only large diesel engines don't have glow plugs but it doen't matter either way as glowplugs are just heaters ant don't produce any electrical noise.

    That and glow plugs are only used to start the engine. Once the engine is running they turn off.

    Unfortunately, I don't know where the noise is communing from.

    Do all alternators produce the a nice sine wave?
  6. You are correct, they are running at 15.5V. If I where to hook them up to the battery directly though, wouldn't they get quieter and quieter as the battery drained?

    I was curious, so I checked the power supply's of my modem, router, and answering machine as well.

    The modem and router are both rated at 12VDC.
    The modem is 17.2V.
    The router is 13.7V.

    The answering machine is rated at 7.5V, but the power supply is supplying 13.2V.

    What I find most interesting about this is the voltage of my incoming power, which is 112V AC. I know a lot of houses, in America anyways, are running closer to 120V AC.
    I guess that means most electronics aren't as picky as I thought they where.

    Still though, my modem is always really hot, maybe I should run it on a lower voltage?

    Should I just get a 15V regulator and call it a day?

  7. Please post a photograph of the waveform.

    I will do that the very next time I get my hands on an oscilloscope.

    Any petrol (gasoline) engine will have an ignition system, even if it has no battery. Diesel engines have glow plugs but no ignition system.

    Sure, but not all diesel engines have glow plugs. This one for example does not.

    The best solution is to just buiy a ready made mains RFI filter.

    I suppose without seeing an actually picture of the output, it is a little hard to tell exactly what kind of distortion it is producing, huh?

    I did hook up a Islatrol active tracking filter which is a "high-frequency noise filter with transient protection for critical loads," but  it had no real effect.

    I will work on getting a picture of the output and continue to hold, one hour at a time, as my call is very important...  ::)
  8. I'm trying to build a basic power supply for a few of my electronics, which include my desktop speakers. My concern at the moment is the voltage dropout rating. I've never built a 12V regulated power supply that runs off of a 12V battery.

    I was looking at a LT1085CT-12 from Digi-Key. It has an input range of less than 25V (I guess that means I don't even need a battery) and a dropout voltage of 1.5.

    This is to run off of a battery that will have a voltage range of about 10.5V to about 14.5V.

    The maintenance charge is about 13.5V. So, assuming a voltage dropout of 1.5, if I hooked up this regulator, would I get 12V?
    What happens when I remove the battery maintainer and the voltage drops to about 13V? Do I all of the sudden get no voltage?
    Is the actual input range 13.5V - 25V and less than 10.5V?


  9. Sorry for the delay, I'm still trying to get a hold of the manufacture of my generator to see what they can do, if anything...

    That's not too bad, it appeard to be EMI, possibly generated by the ignition system

    Well, the graph I made only shows the worst couple of spots. There are spikes and dips along the entire have form. I was just really lazy in drawing the graph. On the good side though, it is very constant. It was almost like looking at a picture on the screen.

    I don't know what you mean by ignition system. I know I didn't specify before, because I wasn't sure what the output rating is, but it is a 6kW pull start generator. As far as I know there is no ignition system. There is no battery and there are no glow plugs...

    [...] An inductor in series and capacitor in parallel will be much better.

    I'm not familiar with AC capacitors and I can only assume you need special inductors for AC as well.

    I do remember building a DC power supply a while back in which I used a very specific formula, some capacitors, and some inductors to get my ripple to basically zero. Is there a different formula I need to follow with AC? I don't want to flat line my AC...

    What kind of capacitors do I need? What kind of capacitance would I need?
  10. I'm not sure if this is the right forum to put this in, I'm not even sure if this is the right site to post this in, but I have a diesel generator that produces 120V AC via a badly regulated alternator. It was actually causing our ACP UPS's to go nuts and click on and off repeatedly. I finally got the chance to hook it up to an oscilloscope and found out why. It looks kind of like a really bad stepped sine wave.
    Here is a really bad illustration of what it kind of sort of almost looks like:

    Unfortunately, I didn't have the foresight to take a picture of it. It has the basic shape of a sine wave and the peaks are at about 175V, but all along the line it had several voltage drops similar to the ones illustrated above. I just showed the worst ones, very little of it, if any, is smooth Like I would expect.

    So, I need to find some way of fixing the power. I would like something that I plug in line between the generator and the switch panel.

    I did find a power conditioner by APC but I don't think this would do what I would like it do, defiantly not on the scale I would like it to work.

    I've read several posts in various forums on this subject and they all seem to say the same thing, you shouldn't have bought such a piece of crap. I was hoping you guys, who seem to be very knowledgeable would be able to provide a better insight.

    Any ideas?
    Why is it so are to make dirty AC pretty?


  11. That sounds reasonable enough to me, but that thing isn't in series with the resistor, it's in parallel... The main reason I wanted to know was because I thought it was some kind of weird voltage regulator or something. I thought it was weird that the AC voltage drops like that without a transformer.

    Now as far as this voltage drop goes, do you know any formulas for calculating this drop based on the value of the components? Perhaps I should ask this somewhere else, the parts request forum is probably not the best place for this sort of thing. I was going to use strait AC for my project, but as it turns out, it would force me to use 180V DC, which is just too much. I was then going to use a transformer to step the voltage down, but finding the right transformer is a major pain! Then, when I saw the little motion night light plugged into the wall, I knew it had to be running on low voltage DC but it wasn't big enough to house a transformer, I took it apart to find that weird little red thing which seems to be lowering the voltage, and I thought eureka!

    That's where I'm at now, thanks for your assistance. I think I will start a thread in project designs / ideas to get a little more assistance with this, unless you object....

  12. Thanks for the reply. That's what I kinda thought it was at first, but shouldn't it say 564KF (minor detail)? Then wouldn't that make it a 564,000F capacitor!? At 400V, that thing would be massive!! I've heard of AC caps, but I always thought they were rare, and expensive. Then I wonder where this huge voltage drop is coming from...

    I didn't think about this before, but the voltage drop I am seeing could be do to the resistor. I don't know for sure, but I'm guessing a resistor on an AC circuit works the same as it does on a DC circuit. 220K ohms doesn't seem like very much though. Maybe I will ask about this in the projects and idea section, because until now, I thought the only way to lower AC voltage was with transformer...

    Another thought that just popped into my frawn (oober Geek!) is what if that thing is a resistor not a cap. 564K ohms seems to be an odd number, and I've never seen a voltage rating on resistors, but I suppose they have to have them.

    Any other thoughts?

  13. I'm not sure what it is, but it appears to take 120V AC and turn it into about 18V AC. The only markings on it are 564K 400V, not very helpful.

    I've taken a couple of photos and drew up a wiring diagram. In the photos, it is the large red thing.

    As far as the schematic goes, R1 is a 100 ohm ceramic resistor and R2 is labeled red red black orange brown, or brown orange black red red. (I'm not sure what value it is...)

    Thanks for your help!

  14. Using a voltage regulator should reduce the line noise. Your best bet would be to isolate the charger from the amp, but I don't know how to do that. If you are going to use a voltage regulator, I would use a fixed regulator and if the battery pack is 14.4V, I would probably use a 15V regulator or something close to it to compensate for voltage drop.

    If you don't mind me asking, what is the stereo for? Is it any better than what one could buy at a store?

  15. Correct me if I'm wrong, but if you reverse the polarity at the motor, won't it spin in the opposite direction? That is, if the motor runs clockwise while positive is connected to positive and negative is connected to negative, won't it run "anticlockwise" while negative is connected to positive and positive is connected to negative?

    If that's the case, then a set of relays should be enough to make it run forwards and backwards. However, as mentioned before, you don't just want to slam the motor in reverse while it is going forward at full speed. You may need to add a timer to the circuit to give the drill time to slow or stop before changing it's direction.

  16. This should be fairly easy to do, I just don't know how to do so, I was hoping someone here could help me out.

    I built a full wave bridge rectifier using 4 diodes. I put 116V AC for my input, and I got 103.8V DC out. I'm trying to figure out what my output is when my input is, for example, 125V AC or 110V AC...

    I could just break out my variable transformer to some 220V and take a few measurements but, as it turns out, I don't have one. lol :'(

    The alternative, of course, is math! If I knew what the output was when the input is at 100V and 120V, I could probably figure out how to calculate the output at 110V. Unfortunately, or perhaps fortunately, my power company doesn't usually fluctuate that much. Well, that doesn't work so well.  ::)

    In case you where curious:
    I have here a transformer with three outputs, 8V, 16V, and 24V. The input was fairly consistent 115.4V AC.
    This is the output:

    At the Transformer	At the Rectifier	Voltage Drop
    25.7V			22.7V			3.0V
    17.5V			15.4V			2.1V
    08.3V			07.1V			1.2V

    My data suggests the their is a correlation between the input voltage and the voltage drop at the rectifier. If you're good at math, you should be able to determine the correlation and create a formula. I'm not one of those people, so carrying on...

    The voltage drop on a diode, as I recall, is .7V but, that doesn't explain the 12.2V drop that I am seeing. However, on the one side I am reading full AC, where as on the other chopped DC. I am assuming it is this choppiness (Ha, choppiness is a real word!) that is giving me the voltage loss. However, I currently have no way of testing this theory.

    If you have a formula for calculating this, please share!

    Does anyone have any other ideas?


  17. Yeah OK, I new there was something different about the two.
    What is the attenuator for? I'm mean, I know what it does, but why do I need it?
    Does anyone have any diagrams / schematics? I checked the project section and they seem to all be wireless modulators.
    Are there any ICs out there that require just a few discrete components?

    I looked online for some wired type modulators and I found some starting at around $40 (USD). If I can save a few bucks by building one, I would probably rather build it. Also, I'm kind of worried that they might just be overlaying the signal from the headphone jack onto the signal from the antenna. That's how my wireless transmitter works. It just overlays the signal. That's the main reason I want it to be wired, so I can simply cut the antenna out of the picture and get none choppy, none static, consistent audio. I also figure if I can build it for around 10 bucks, I would build a second one for my truck too. I also have a friend who wouldn't mind one either.

    So, if anyone can assist me in build one, I would be very great full!


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