All About Circuits Forum http://forum.allaboutcircuits.com/ A discussion forum for electronics and circuits en Thu, 17 May 2012 00:22:14 GMT vBulletin 60 http://forum.allaboutcircuits.com/images/misc/rss.jpg All About Circuits Forum http://forum.allaboutcircuits.com/ Determine Resistor Value in circuit with a diode http://forum.allaboutcircuits.com/showthread.php?t=70131&goto=newpost Thu, 17 May 2012 00:09:52 GMT I'm ashamed to ask because I actually finished the entire course this problem is from (6 years ago), and because I'm probably missing the obvious, but how would I go about determining the value of R2 in this circuit in order to make 0.25mA flow through the diode?



I'm hoping this can be done without advanced analysis, because I have only refreshed my memory to include thevenin, norton, and ohm's law, but that's where I'm at in the book.

By The way, I know the anser is 24K Ohms, but I don't know how to figure that out without peeking at the answer. ]]> Homework Help DigiDan http://forum.allaboutcircuits.com/showthread.php?t=70131 Discontinued Diodes http://forum.allaboutcircuits.com/showthread.php?t=70130&goto=newpost Wed, 16 May 2012 22:59:44 GMT I'm rebuilding several old power supplies from the 80's. They are used to power working DAC computers from Optim. The problem is, I can't find the data sheet on the 1N758 diode used for voltage regulation. I can't find the actual diode either. Any one know where I can get either or both??

Thanks for the help

Hdohn ]]> Electronics Resources HDohn http://forum.allaboutcircuits.com/showthread.php?t=70130 Strobe Circuit for Pulse Coil http://forum.allaboutcircuits.com/showthread.php?t=70129&goto=newpost Wed, 16 May 2012 19:47:48 GMT Dear Forum, I am using the attached circuit for firing a pulse coil. I would like to replace the Xenon Flash Tube with an SCR to lower the series... Dear Forum,
I am using the attached circuit for firing a pulse coil. I would like to replace the Xenon Flash Tube with an SCR to lower the series resistance.
Can anyone suggest how to do this?
Thanks!
Mike
:)
Attached Files
File Type: doc Strobe Pulser.doc (1.00 MB)
]]> The Projects Forum Cburg http://forum.allaboutcircuits.com/showthread.php?t=70129 Creating A Wire Cut Detection http://forum.allaboutcircuits.com/showthread.php?t=70128&goto=newpost Wed, 16 May 2012 18:53:02 GMT Hello I want to create a wire cut detection circuit for my micro controller and I'm not sure the what the best way is to do this without frying my microcontroller out.

This is basically how I kinda imagine it working:

Pump 24v through a line (since the line is maybe going to be going longer then 100 ft).

Have a EOL resistor of 4.7k at the end of the line and have my trigger/switches in paralleled within the line and of course have a 100 1/4 watt resistor in series.

Then have a some sort of ADC circuit that takes the 24 volts drops it down to 5 and gives us 3 pin binary outputs of the lines state based on voltage output.
2= We are okay, 0 = Line was cut, 3 = Alarm. ]]> General Electronics Chat ajm113 http://forum.allaboutcircuits.com/showthread.php?t=70128 Charging lead acid battery bank http://forum.allaboutcircuits.com/showthread.php?t=70127&goto=newpost Wed, 16 May 2012 18:26:44 GMT I have 6 12 volt car batteries hook up to produce 72v. I have seen chargers that can be connected to each battery and charged at 12v each while the... I have 6 12 volt car batteries hook up to produce 72v. I have seen chargers that can be connected to each battery and charged at 12v each while the batteries are still series and using the 72v from them. But they are expensive. What kind of circuit would it take to do this from 12v to charge the batteries while still using the 72v.
Thanks Ed ]]> General Electronics Chat edwilliams http://forum.allaboutcircuits.com/showthread.php?t=70127 Worksheets Help Why My Uninterrupted Power Supply Need to be slapped EveryTime To charge ? http://forum.allaboutcircuits.com/showthread.php?t=70126&goto=newpost Wed, 16 May 2012 18:23:13 GMT I've installed a UPS for my house (220V mains), connected with 2 car batterys. In my area the daily power outage is 4 hours, So When the power is out, my rooms and computer still function from the UPS. but suddenly the Red Light Of the Charger that is Called ( MAIN ) is not On even when there's electricity . so i climb to my UPS and Slapped or give it a physical Impact ,In order for The Red light to Function, but after some time the light go off again and need to be reforced . Any Suggestion on what is causing this ?? I send it a technician 2 times and he was not able to solve my problem:(
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]]> General Electronics Chat jihadsamarji http://forum.allaboutcircuits.com/showthread.php?t=70126 What I did last Fall/Winter http://forum.allaboutcircuits.com/showthread.php?t=70125&goto=newpost Wed, 16 May 2012 18:07:33 GMT I have not had much time to get on here for a while, but I thought I would stop in and show off my latest project that I completed last winter.... I have not had much time to get on here for a while, but I thought I would stop in and show off my latest project that I completed last winter. project has a few electronic components but it has over 2000 lbs of carbon steel!

I had been getting tired on how natural gas and LP gas prices have been skyrocketing in the past few years, and it had gotten to the point where I would spend up to $1,400.00 a winter on LP Gas.... so I decided to build me an out door wood burning boiler system to heat my house, I have plenty of resources for good firewood so I said why not?
But once I got started on the project, I decided to go one more step, and create a "smokeless" outdoor wood boiler.....

So this is what I ended up with, a smokeless wood gassification outdoor wood boiler.... I built it for a little over $600.00, although a comparable one on the market would have cost me $12,000.00!! And so far, I have spent $65.00 all winter to heat my 3600 sq ft home...

Attachment 42943

View of smoke stack and Primary combustion area:
http://youtu.be/-fZHdCscsE4

View of secondary burn area:
http://youtu.be/K3CLAs5ECb8


This unit basically has 2 combustion chambers, the primary chamber "gassifies" the wood almost to the point of pyrolysis, the "smoke" is then drawn back through the hot coals to heat it up to 1100 degrees, which at that point super heated combustion air is injected and mixed with the heated gas which is then burned in the secondary chamber that burns up to 2200 degrees..... :D
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]]> Off-Topic BMorse http://forum.allaboutcircuits.com/showthread.php?t=70125 Tesla coil cap question http://forum.allaboutcircuits.com/showthread.php?t=70124&goto=newpost Wed, 16 May 2012 17:28:02 GMT im working on the tank capacitor for my spark gap tesla coil. i just had a quick question. i doubt i will find the ideal capacitance i need of 8.6nF....
im working on the tank capacitor for my spark gap tesla coil. i just had a quick question. i doubt i will find the ideal capacitance i need of 8.6nF. if i cant find the exact, but a close value, would it be better to error on the high side or error on the low side of 8.6nF?
]]> General Electronics Chat lokeycmos http://forum.allaboutcircuits.com/showthread.php?t=70124 Help with Designspark http://forum.allaboutcircuits.com/showthread.php?t=70123&goto=newpost Wed, 16 May 2012 17:07:34 GMT Hi all.

I'm currently designing a project in Designspark.

However, I need to split the project, and connect sections with little arrows (apologies for not knowing the name).

Could someone please suggest a means of doing this, so that when routing the pcb, it reliases that they should be connected?

Many thanks,

Sparky ]]> General Electronics Chat Sparky49 http://forum.allaboutcircuits.com/showthread.php?t=70123 BJT in saturation http://forum.allaboutcircuits.com/showthread.php?t=70122&goto=newpost Wed, 16 May 2012 17:04:19 GMT I'm having a hard time understanding the concept of BJTs in saturation and active mode. So far I have got that the base-emitter junction is forward biased, so electrons go from the emitter to the base, where some of them recombine, but most of them diffuse to the collector as there is a concentration gradient.

But, during saturation the base-collector junction is reverse biased, so my question is how can current flow out of the collector in the first place? And why does it stop increasing (apart from the Early effect which I do understand) when VCE~0.7 i.e. it becomes forward biased? I have read that it's because VBC is decreasing as VCE increases, and after VCE~0.7 VBC cannot get any smaller, which does make sense, so I suppose the main question is how Ic comes about.

I know this is a common question and I have spent a long time reading many posts of forums but nothing I have read fully explains it to me. I would like to know physically what is happening in the BJT, and what is meant by 'saturation' and 'active'. ]]> General Electronics Chat ebyrne288 http://forum.allaboutcircuits.com/showthread.php?t=70122 James Bond CIA Gadget Challenge http://forum.allaboutcircuits.com/showthread.php?t=70121&goto=newpost Wed, 16 May 2012 17:03:48 GMT Hey guys, The other day my friend and I got into a debate about Bond/CIA gadgets and he swears its impossible to create a lethal tazer small... Hey guys,

The other day my friend and I got into a debate about Bond/CIA gadgets and he swears its impossible to create a lethal tazer small enough to hide inside the housing of a ballpoint pen. I came here to get some help from the professionals! Can someone please give me enough information on this (some equations or components list, etc.) so I can prove to him its possible? Any help is really appreciated because we have a pretty stiff bet on this.

Thanks! ]]> General Electronics Chat joel85 http://forum.allaboutcircuits.com/showthread.php?t=70121 DPDT momentary/off/on wiring question http://forum.allaboutcircuits.com/showthread.php?t=70119&goto=newpost Wed, 16 May 2012 16:52:33 GMT I know almost nothing about wiring and electronics, so bear with me. I have a set of 3-wire, flashing LED lights that I need to wire up. They work... I know almost nothing about wiring and electronics, so bear with me.

I have a set of 3-wire, flashing LED lights that I need to wire up. They work in such a way that red is power and black is ground. The third wire, yellow, will change the flash pattern of the LEDs when connected to the power source for a moment. For this to work the unit must already be "on" (i.e. the red wire is already connected to power)

So here's what I'm thinking: get a DPDT switch with momentary on/ off/ constant on. Then, wire it in such a way that the unit will be "off" when the switch is in the "down" position, will be "on" when in the center position, and will change the flash pattern when flipped to the momentary "up" position.

Attached is how I *think* the switch needs to be wired for this to work, but I really have no idea. Am I far off the mark here?

Also, with the DPDT, will there be a brief break in current when I go from "on" to "momentary," such that it will turn the unit off and thus negate the ability of the unit to stay "on" as I try to switch phases?

]]> General Electronics Chat DHB http://forum.allaboutcircuits.com/showthread.php?t=70119 Sony KP-53S65 rear projection tv http://forum.allaboutcircuits.com/showthread.php?t=70118&goto=newpost Wed, 16 May 2012 16:07:03 GMT Hello, Can someone tell me how to remove the high tension leads from the flyback transformer. I have to remove the boards so I can replace the... Hello, Can someone tell me how to remove the high tension leads from the flyback transformer. I have to remove the boards so I can replace the STK392-150 IC Chips. ]]> General Electronics Chat mactech http://forum.allaboutcircuits.com/showthread.php?t=70118 Low current sensor using LTC6102 http://forum.allaboutcircuits.com/showthread.php?t=70117&goto=newpost Wed, 16 May 2012 16:03:06 GMT Hello everyone,
objective: I am actually trying to design a curent sensor ranging from 1uA to 1A. I know it won't be possible with only one sensing resistor but my problem is to sense the 1uA.

Here are my concerns (the schematic is joined):

1) The offset voltage of the LTC6102 sense amplifier should be no more than 10uV(cf datasheet) but when i simulate with a load current of 0A, I can read an offset voltage of 20-25uV.

2) If we admitt the offset voltage is 20uV, by choosing a 100ohm sense resistor, the Current offset should be 0.2uA max. The maximum sensing voltage is given in the datasheet: 2V max which means that we can sense up to 20mA.
But, when simulating with a 1mA load current instead of having (almost) 1mA through Rin, I only have 56mA. This is due to a difference of voltage between Vsense=5.900V and Vin=5.943V which should normally be (almost) equal.

Please any help his welcome!!

regards,

charles

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]]> General Electronics Chat xkekex http://forum.allaboutcircuits.com/showthread.php?t=70117 Oscilloscope Probe Frequency http://forum.allaboutcircuits.com/showthread.php?t=70116&goto=newpost Wed, 16 May 2012 15:54:23 GMT Hi all, I just got a loan of an oscilloscope but have to purchase my own probes. It is a 100MHz scope.

Do the probes have to match the scope's frequency to work properly or can I use 60MHz probes? I'm thinking 60MHz probes would just limit my range to a maximum of 60MHz, but I'd like to clarify this before unnnecessarily wasting money.

Thanks,
Winger ]]> Electronics Resources djwinger http://forum.allaboutcircuits.com/showthread.php?t=70116