Help! What is it? Capacitor?

Started by Ivan Vegvary in sci.electronics.design6 years ago 13 replies

Sorting through a grab bag of capacitors, reading labels and also checking with multimeter. Ran across a handful of the following marked...

Sorting through a grab bag of capacitors, reading labels and also checking with multimeter. Ran across a handful of the following marked thus: "Sprague, 30D+, TE1129, 15-12DC, USA +, 8124H" Small metalic cylinders measuring approximately 1/4" round and 1/2" long. Possibly inductors, but 8124 Henries seems rather large. Thank you for replies. Ivan Vegvary


Parasitics?

Started by rickman in sci.electronics.design6 years ago 18 replies

I'm running a simulation where I'm pumping charge into a capacitor to generate a voltage. A transistor emitter/source is connected to the...

I'm running a simulation where I'm pumping charge into a capacitor to generate a voltage. A transistor emitter/source is connected to the positive rail and the collector/drain is connected to a 1 nF cap through a 47k resistor. When the base/gate is driven high to shut off the current I see the current go up initially then taking almost 2 us to shut off. I've tried 2N3906 and BSS84 and...


bad, better delay circuits

Started by John Larkin in sci.electronics.design6 years ago 35 replies

We want to trim the rising edge times of some pulses. The obvious circuit is a current source + capacitor linear ramp followed by...

We want to trim the rising edge times of some pulses. The obvious circuit is a current source + capacitor linear ramp followed by a comparator. The first circuit here was the initial idea, seems simple, until I started thinking harder. https://dl.dropboxusercontent.com/u/53724080/Circuits/Timing/Delay_Bad_Good.JPG BSS123 is about the best compromise between capacitance and ON resi...


Gain of FET circuit

Started by amdx in sci.electronics.design5 years ago 63 replies

Hi Guys, I have a FET replacement circuit for a tube. I want to know what the Gain of the FET circuit is. Here's the schematic of the FET...

Hi Guys, I have a FET replacement circuit for a tube. I want to know what the Gain of the FET circuit is. Here's the schematic of the FET circuit. > https://www.dropbox.com/s/5k6581ch0rwqxiv/Boonton%20tube%20replacement%20plus%20load.jpg?dl=0 Can you calculate the Voltage Gain from Gate to Source. The gate will be connected to a capacitor with 1.2mV to 5mV RMS on it.


The linear Diode Detector

Started by amdx in sci.electronics.design5 years ago 89 replies

Hi guys, I'm now moving to the diode detector that I want linear over a 10 to 1 range. Say 0.5v input to 5v input or .75v input to 7.5v...

Hi guys, I'm now moving to the diode detector that I want linear over a 10 to 1 range. Say 0.5v input to 5v input or .75v input to 7.5v input. As it stands my amp has a 470 ohm output impedance, I will adjust as needed. I found this article, that I think does what I want. However it is tested a 900Mhz, I'm happy to get to 10MHz. Do I scale the capacitor scale with frequency? (.04...


Pre-war capacitor

Started by Anonymous in sci.electronics.design5 years ago 4 replies

I have an old EHT PSU to repair. There are 2 capacitors, one paper, one plywood! The paper cap, which is uncased, tests as: 420nF 11 ohms ESR, 5%...

I have an old EHT PSU to repair. There are 2 capacitors, one paper, one plywood! The paper cap, which is uncased, tests as: 420nF 11 ohms ESR, 5% loss. I've not yet done a dc leak test, which it needs. What do you think of those figures? IME pre-war paper caps are highly suspect. I'd rather establish what I can before subbing it, as the construction of the whole thing is rather char


200kHz oscillator

Started by Piotr Wyderski in sci.electronics.design5 years ago 11 replies

I would like to experiment a bit with magnetic parametric amplifiers. For that purpose, I believe I need a 200kHz sine wave generator with a...

I would like to experiment a bit with magnetic parametric amplifiers. For that purpose, I believe I need a 200kHz sine wave generator with a watt worth of output power. My obvious choice was to construct a current-fed resonant Royer oscillator. For a 1nF tank capacitor it implies a 633uH inductor (2x5 turns on a 6400nH/turn^2 way to big toroidal core), 2x ZTX851, a 100k base polarization resi...


Problem - how to discharge a capacitor ONLY after the voltage has dropped to around 6VDC.

Started by John Robertson in sci.electronics.design5 years ago 44 replies

Interesting problem (at least I think so). We have a situation where a tiny (5VDC @ 5A) switching supply that takes roughly 8 to 15VDC in and...

Interesting problem (at least I think so). We have a situation where a tiny (5VDC @ 5A) switching supply that takes roughly 8 to 15VDC in and converts it to 5VDC out, however the regulator won't boot unless the input voltage falls below 4.xxVDC prior to power back on, otherwise the device just sits there and plays dead/off. When the input power is shut off the voltage across the input ...


FYI: 0603 Capacitor Kit

Started by Wanderer in sci.electronics.design5 years ago 1 reply

I bought this capacitor kit. http://www.surplusshed.com/pages/item/r3856.html It comes in a nice box with little vials and at least 30 of...

I bought this capacitor kit. http://www.surplusshed.com/pages/item/r3856.html It comes in a nice box with little vials and at least 30 of each value. (I didn't count them)


The 280 pound capacitor

Started by Cursitor Doom in sci.electronics.design5 years ago 36 replies

Hi all, I tore down a Marconi signal generator today. It's been awaiting my attention for quite a while. Can't recall the model number off...

Hi all, I tore down a Marconi signal generator today. It's been awaiting my attention for quite a while. Can't recall the model number off hand but it does 10kHz to 5.4Ghz IIRC. I bought it from some chap who told me it had a faulty smoothing cap in the PSU 'cos it was generating signals with ripple on it. He told me he'd been quoted GBP280 ($387 in US dough as of today's date) for a ...


Placing Tesla Coil Capacitor WITHIN the Secondary

Started by Robert Miller in sci.electronics.design5 years ago 7 replies

I intend to build a classic spark gap Tesla coil. I understand the value of the timing cap must be selected with reference to the resonant...

I intend to build a classic spark gap Tesla coil. I understand the value of the timing cap must be selected with reference to the resonant frequency of the coil. I was wondering what would happen if I was to custom build (wrap) a tubular cap, from al foil and mylar, and slide it _within_ the TC's secondary so both are on the same axis. Would this configuration tend to make selection ...


Fusible resistor (sort of)

Started by bitrex in sci.electronics.design5 years ago 2 replies

I made a wrong connection in finishing off restoring my Heathkit IT-11 capacitor checker, which caused the full 600 volt B+ to be applied...

I made a wrong connection in finishing off restoring my Heathkit IT-11 capacitor checker, which caused the full 600 volt B+ to be applied across this old 560 ohm 1/2 watt carbon comp resistor: https://www.dropbox.com/s/nr948ci7j3kz52t/20170628_125738.jpg?dl=0> Enormous amounts of magic smoke came out of it, but after ~50 years of waiting the original glass fuse did its job and opened m


Recognise this trace?

Started by Cursitor Doom in sci.electronics.design5 years ago 32 replies

Gentlemen, The link below shows a scope trace of the output of a linear PSU (voltage 4.7VDC) with about 300mV of 100Hz ripple riding on it....

Gentlemen, The link below shows a scope trace of the output of a linear PSU (voltage 4.7VDC) with about 300mV of 100Hz ripple riding on it. This PSU is in- circuit under load from the boards it supplies. Normally I would assume a filter capacitor to be at fault here, but they all check out fine so something else is causing this ripple. Note there is a characteristic 'knee' on the high ...


PI controller capacitor

Started by Michael in sci.electronics.design5 years ago 27 replies

MLCC capacitors are not recommended because of piezo-effect related noise. How bad/serious is it? I haven't used ceramics in this application...

MLCC capacitors are not recommended because of piezo-effect related noise. How bad/serious is it? I haven't used ceramics in this application yet. I need time constant in the order of tens of seconds. Cannot find tantalums with high enough RC specs, film caps are too big. Any suggestions - ? Thank s!


Electrolytic cap reverse voltage?

Started by billbowden in sci.electronics.design5 years ago 16 replies

What is the maximum reverse voltage a polarized electrolytic capacitor can withstand? I have a 1uF electrolytic cap rated at 50 volts. Is it...

What is the maximum reverse voltage a polarized electrolytic capacitor can withstand? I have a 1uF electrolytic cap rated at 50 volts. Is it safe to reverse charge this cap to 1.5 volts? .


Physicists detect radio waves with light

Started by amdx in sci.electronics.design5 years ago 12 replies

"The new approach is simple in principle. Their device consists of a thin membrane of silicon nitride coated with a mirror-like layer of...

"The new approach is simple in principle. Their device consists of a thin membrane of silicon nitride coated with a mirror-like layer of aluminium. This nanomembrane is suspended above an electrode forming a capacitor which is itself part of a standard LC-circuit that picks up radio waves at its resonant frequency. When this happens, the resonating circuit causes the nanomembrane to...


Help Please -- very strange oscillator problem

Started by Anonymous in sci.electronics.design5 years ago 34 replies

Could some electronics guru please help ? I have two identical(same resistor, capacitor values) implementations of an astable multivibrator. I...

Could some electronics guru please help ? I have two identical(same resistor, capacitor values) implementations of an astable multivibrator. I am using the 2N3055 and each transistor drives a coil each of a bifilar coil, whose common terminal is connected to a 12 Volt 2A(max) DC power supply. The coils is air core. The problem is that one implementation works as designed, the other does ...


How to use a boost cap to kickstart a relay with low voltage

Started by Don Kuenz in sci.electronics.design4 years ago 22 replies

The DC voltage on many (all?) ham radio power supplies tops out at about 14VDC. So what do you do when you find the perfect relay, but...

The DC voltage on many (all?) ham radio power supplies tops out at about 14VDC. So what do you do when you find the perfect relay, but it only comes in the 24VDC or 28VDC pull-in flavor? "Using Direct-Current Relays at Lower Coil Voltages" (KE0FF), in the current issue of _QEX_, talks about how to use a boost capacitor to kick start a relay using a voltage lower than the pull-in vol...


Analog MUX using discrete MOSFETs for flying capacitor cell measurement BMS

Started by P E Schoen in sci.electronics.design5 years ago 20 replies

My latest project is a battery management system (BMS) that can accurately measure cells in a lithium battery pack, and also perform shunt...

My latest project is a battery management system (BMS) that can accurately measure cells in a lithium battery pack, and also perform shunt balancing and possibly charge shuttling to balance the pack. I would also like to be able to use it for a pack of four 12V SLA batteries. A DG408 could be used to select up to 8 cell voltage taps from nominal 3.2V (LiFePO4) or 3.7V (Li-Ion), with a ma...


Using matched pair PNP BJTs and analog MUX to measure cells in battery pack

Started by P E Schoen in sci.electronics.design5 years ago 8 replies

My previous post was for an analog MUX using discrete MOSFETs and a flying capacitor for voltage measurement of the cells in a battery pack....

My previous post was for an analog MUX using discrete MOSFETs and a flying capacitor for voltage measurement of the cells in a battery pack. That seems to be a workable design and I am going to get some prototype PCBs made to prove the concept. But I also considered a design using a DG409 (for 4 cells) or two DG408s (for 8 cells). To do that properly involves an instrumentation amplifier...