Constant Voltage Transformer Operation?

Started by amdx in sci.electronics.design9 years ago 7 replies

I recently repaired a marine battery charger. It was set up to charge 3 separate 12v batteries. The repair was simple the charger had a...

I recently repaired a marine battery charger. It was set up to charge 3 separate 12v batteries. The repair was simple the charger had a *shorted 40uf 660v ac capacitor. The capacitor is connected across a winding on the transformer. This is the usual constant voltage transformer configuration. This is the extent of what I think I know. Can someone describe the operation of a constant vo...


fast ramp follies

Started by John Larkin in sci.electronics.design4 years ago 139 replies

OK, I need to charge a capacitor with a stable constant current. The desired slope is about a volt per nanosecond. So I did...

OK, I need to charge a capacitor with a stable constant current. The desired slope is about a volt per nanosecond. So I did this: https://dl.dropbox.com/u/53724080/Circuits/Fast_Ramp.JPG Things like this tend to oscillate, so I used a fairly slow, high-beta transistor, BCX71K. The ferrite in the collector is supposed to isolate the ramp cap from the transistor capacitance and make ...


Digital Stream DTV converter failed

Started by Anonymous in sci.electronics.design9 years ago 15 replies

I bought it several years ago, but it was just in the closet as a spare. I've only used this DTV converter for a couple months. Today...

I bought it several years ago, but it was just in the closet as a spare. I've only used this DTV converter for a couple months. Today it suddenly just shut off and left snow on the tv screen. If I unplug it, the front LED lights for a second and shuts off. I'm suspecting a capacitor.... Anyone know of a common problem with these converters? Thanks


Need some advice on RC characteristics of Slope ADC

Started by Myauk in sci.electronics.design9 years ago 20 replies

Hi All, As I am working on Slope ADC configuration as described by...

Hi All, As I am working on Slope ADC configuration as described by AN863 (http://ww1.microchip.com/downloads/en/AppNotes/00863a.pdf) Microchip application note AN929 http://ww1.microchip.com/downloads/en/AppNotes/00929a.pdf , page 3 figure 5 shows Ramp Rate Method where by using a single Capacitor and a known ref: resistor, the resistance of any unknown resistor Rx can be measured. The met...


Tantalum capacitor ESR

Started by Cursitor Doom in sci.electronics.design2 years ago 29 replies

Gentlemen, I took a crazy risk and got some axial Kemet tantalums off Ebay (purportedly genuine). These are visually identical to the...

Gentlemen, I took a crazy risk and got some axial Kemet tantalums off Ebay (purportedly genuine). These are visually identical to the originals out of one of my HP boat anchors. And the ESR figures are better than the equivalent new aluminium (aloominum if you're in the US) electrolytics. But are these ESRs low enough to be the real thing? Here's an example of the values I'm seeing: 3.3...


what does the Q2 do in this CCD preamplifier?

Started by Anonymous in sci.electronics.design9 years ago 7 replies

http://instrumentation.obs.carnegiescience.edu/ccd/gcam/images/PRE_SCH.jpg looks like Q2 is a clamp reset to zero voltage reference ,i.e. the...

http://instrumentation.obs.carnegiescience.edu/ccd/gcam/images/PRE_SCH.jpg looks like Q2 is a clamp reset to zero voltage reference ,i.e. the ground. However, the ccd signal is changing rapidly , for example, within 1us the ccd has a signal like ILX511B (http://www.oceanoptics.com/technical/ILX511B%28E%29.pdf) and within this time constant the capacitor didn't ground due to the long time cons...


capacitor COE question

Started by John Larkin in sci.electronics.design9 years ago 34 replies

If a capacitor has a largish temperature coefficient (hundreds of PPM capacitance change per degree C maybe), what happens to a charged...

If a capacitor has a largish temperature coefficient (hundreds of PPM capacitance change per degree C maybe), what happens to a charged cap when the temperature changes? Presumably C*V stays constant, so the stored energy 0.5*C*V^2 changes. So, would the specific heat of the capacitor be different, as a function of whether it is charged or not? -- John Larkin ...


C0G ceramics vs humidity---I think I have the answer

Started by Badbob in sci.electronics.design7 years ago 1 reply

Follow my logic: The reason a polymer capacitor drifts with a change in humidity is that water is a very polar molecule w/ a dielectric...

Follow my logic: The reason a polymer capacitor drifts with a change in humidity is that water is a very polar molecule w/ a dielectric constant of about 80. Polymers are much lower, 2-8 more or less. Add .1% water to the plastic and you get a large change in d constant, around 4%. C0G material has a constant that varies but usually similar to water. Add .1% water and you get a ch...


Dots on inductors

Started by Raveninghorde in sci.electronics.design9 years ago 20 replies

I read many years ago (National app note from memory) that one should connect the inner layer of an inductor to the switch in a buck regulator...

I read many years ago (National app note from memory) that one should connect the inner layer of an inductor to the switch in a buck regulator and the outer layer to the capacitor as the outer layer will then act as a screen. I don't know if it makes a difference in practice but it's free. With many modern inductors it is impossible to see how they are wound so the only indication of "po...


hi my name is kael

Started by kael in sci.electronics.design9 years ago 9 replies

he gave me a resistor of hundred kilo eum and a capacitor to repair my electric heart How do I conect this?

he gave me a resistor of hundred kilo eum and a capacitor to repair my electric heart How do I conect this?


what exactly is a flux capacitor?

Started by kael in sci.electronics.design9 years ago 25 replies

what exactly is a flux capacitor, and why does my watch run backward when I reverse the magitic field?

what exactly is a flux capacitor, and why does my watch run backward when I reverse the magitic field?


Super super capacitor:?

Started by Jan Panteltje in sci.electronics.design9 years ago 30 replies

Super super capacitor: http://www.sciencedump.com/content/super-supercapacitor

Super super capacitor: http://www.sciencedump.com/content/super-supercapacitor


I thought I was smart enough

Started by amdx in sci.electronics.design2 years ago 6 replies

I'm try to help the guy with the LDR triggering a 555. I'm slowly walking him through it and now just triggering it with a wire momentarily to...

I'm try to help the guy with the LDR triggering a 555. I'm slowly walking him through it and now just triggering it with a wire momentarily to grd, to pull Pin 2 low, through a capacitor. But it won't trigger. Here's the circuit, what is needed to make the circuit trigger properly. > https://www.dropbox.com/s/fwxu5vqazzqist4/one%20shot%20wire.jpg?dl=0 Ignore the LDR for now I realize


Graphene Micro Supercapacitors

Started by amdx in sci.electronics.design9 years ago 7 replies

An interesting article about micro capacitor manufacturer. "These micro-supercapacitors, made from a one-atom-thick layer of graphitic...

An interesting article about micro capacitor manufacturer. "These micro-supercapacitors, made from a one-atom-thick layer of graphitic carbon, can be easily manufactured and readily integrated into small devices such as next-generation pacemakers" http://www.sciencedaily.com/releases/2013/02/130220100755.htm Mikek


Ceramic capacitor value changes drastically with DC bias

Started by JW in sci.electronics.design9 years ago 42 replies

I don't think I've seen this discussed before - I did not know...

I don't think I've seen this discussed before - I did not know this. http://www.edn.com/design/analog/4402049/Temperature-and-voltage-variation-of-ceramic-capacitors --or-why-your-4-7--F-capacitor-becomes-a-0-33--F-capacitor


Gas-tube spark arrestor as RF pulse-modulator?!

Started by Bill Beaty in sci.electronics.design9 years ago 3 replies

I find some SMT mystery components on a few-watts RF pulse board for an NMR probe driver. Little white ceramic cylinders with gold end caps,...

I find some SMT mystery components on a few-watts RF pulse board for an NMR probe driver. Little white ceramic cylinders with gold end caps, maybe 0.1" diameter. But they're wired *across* a 50-ohm pcb trace, and driven by some 500V FETs via a resistor chain and one HV capacitor. WTF? Huh. What if these are spark gaps? If the designer chose several different voltages, then one DC ...


simple capacitor test circuit

Started by Anonymous in sci.electronics.design9 years ago 32 replies

Hello, I am new to discussion groups. I have a home built capacitor (it sho= uld have a fairly large capacitance) and I would like to find out...

Hello, I am new to discussion groups. I have a home built capacitor (it sho= uld have a fairly large capacitance) and I would like to find out what its = value is as accurately as possible with a standard multimeter. I wonder if = it is possible to build a simple circuit with a led light indicator or some= thing that with a little math and good capacitors can tell me ruffly how la= rge it is....


SUPER CAPACITOR STEP UP POWER SUPPLY

Started by RealInfo in sci.electronics.design9 years ago 9 replies

Hi all In case I use some super capacitors with very high capacitance like 10s of farads in parallel and those capacitors can be charged...

Hi all In case I use some super capacitors with very high capacitance like 10s of farads in parallel and those capacitors can be charged to 2.7 volts max, how do I step up that low volt to constant 24 vdc , high currnet ? The main problem is that the 2,7 volt decreases to almost zero gradually . So how I keep a constant 24 vdc while capacitor voltage goes down ? Thanks ...


Purpose of precision high-current series regulator's resistors and capacitor?

Started by Don Kuenz in sci.electronics.design2 years ago 32 replies

This question was originally posted to piclist. The TL431 datasheet contains "Figure 29. Precision High-Current Series Regulator." What's the...

This question was originally posted to piclist. The TL431 datasheet contains "Figure 29. Precision High-Current Series Regulator." What's the purpose of the 30 ? resistor, the 4.7 k? resistor, and the 0.01 ?F capacitor? Thank you, -- Don Kuenz KB7RPU There was a young lady named Bright Whose speed was far faster than light; She set out one day In a relative way And returned on


Crapacitors

Started by Anonymous in sci.electronics.design9 years ago 75 replies

4.7uF 6.3V X5R dC = -70% @ 6VDC (!!) http://psearch.murata.com/capacitor/product/GRM188R60J475ME19%23.pdf James

4.7uF 6.3V X5R dC = -70% @ 6VDC (!!) http://psearch.murata.com/capacitor/product/GRM188R60J475ME19%23.pdf James