Filter Cap for a battery pack ?

Started by Sid 03 in sci.electronics.design11 months ago 5 replies

I need to select a capacitor for a battery pack. I see a lot of circuits that use Alkaline batteries and then have a ceramic capacitor across the...

I need to select a capacitor for a battery pack. I see a lot of circuits that use Alkaline batteries and then have a ceramic capacitor across the leads of the series battery pack to act as a filter. My question is how do you size the cap ? I hate just looking at what someone else has done and just guess or copy. I have 4x 1.5v alkaline batteries in series powering a amplifier circuit. ...


that weird T502 board

Started by John Larkin in sci.electronics.design11 months ago 3 replies

We finally got a batch of boards. https://www.dropbox.com/s/rul9yep9ys0snyo/T502A_PCB.jpg?raw=1 None of the board houses minded making the...

We finally got a batch of boards. https://www.dropbox.com/s/rul9yep9ys0snyo/T502A_PCB.jpg?raw=1 None of the board houses minded making the three v-score breakaways. Tiny, in this case some 50 mil high, reference designators don't seem to be a problem these days. These look ink-jet printed to me. My test capacitor is upper-right, layer 1 to the layer 2 ground plane. If the board was f...


Digital transistor?

Started by Sylvia Else in sci.electronics.design8 months ago 13 replies

https://www.farnell.com/datasheets/2353855.pdf I bought a few of these. I don't know what is intended by "digital transistor" since the...

https://www.farnell.com/datasheets/2353855.pdf I bought a few of these. I don't know what is intended by "digital transistor" since the charge storage time defeats any attempt to use them at a high frequency, and there's no way to add a Schottky diode to prevent saturation, or a speed-up capacitor across the base resistor. I'm using this and the corresponding PNP type to do level shift...


power supply subtelties

Started by Anonymous in sci.electronics.design5 months ago 14 replies

I never thought a lot about general-purpose bench type power supplies, but now we have to design some. A power supply has two knobs (or SCPI...

I never thought a lot about general-purpose bench type power supplies, but now we have to design some. A power supply has two knobs (or SCPI commands in our case), voltage and current limit. A power supply should have low impedance at high frequencies, so after whatever current limit circuit is has, there must be a real capacitor. When you short a bench supply, you get a spark from the e...


pad-to-pad capacitance

Started by sea moss in sci.electronics.design4 months ago 8 replies

Two part question (my google skills have failed me for both): 1. Does anyone know approximate pad-to-pad capacitance for the common SMD...

Two part question (my google skills have failed me for both): 1. Does anyone know approximate pad-to-pad capacitance for the common SMD packages (0201, 0402, 0603, 0805)? Ever measured it? I can't use the parallel plate capacitor formula, since the plates are adjacent, not parallel. (assume there is no copper below the pads) 2. Given an SMD footprint as above, how close does a g


Measuring the Disspation of the self capacitance of a thru hole resistor.

Started by Lamont Cranston in sci.electronics.design7 days ago 44 replies

I have added a 10MΩ resistor across a high Q LC (on a Q meter) and did the math on the drop in Q to get the value, but instead of 10MΩ I...

I have added a 10MΩ resistor across a high Q LC (on a Q meter) and did the math on the drop in Q to get the value, but instead of 10MΩ I got 4,280,000Ω. I'm tuning out the self capacitance, but think maybe I have the loss resistance multiplied by the Q of the resistors self capacitor (9,342,398Ω) in parallel with the 10MΩ giving me the low measurement of 4,2


PCN Process and Notification Specification

Started by Ricky in sci.electronics.design1 day ago 1 reply

I'm being asked by a potential customer if I'm familiar with "PCN process and notification". My company does not normally make changes to...

I'm being asked by a potential customer if I'm familiar with "PCN process and notification". My company does not normally make changes to products other than to substitute components that are functionally equivalent. A different brand of resistor, or capacitor, sometimes chips, are used when the original part is not available. I don't generate a PCN for such changes. Is th


Abiding by the USB 100mA, 500mA rule

Started by Winfield Hill in sci.electronics.design3 years ago 18 replies

Struggling to meet strict USB current-draw rules. Some of the problems start with small TI buck and boost converters that use the Peak...

Struggling to meet strict USB current-draw rules. Some of the problems start with small TI buck and boost converters that use the Peak Current Control method, with the input current always ramping up to a high maximum value. Multiple converters run from the supply, and capacitors C1 C2 = 100uF try to average the current to under 500mA. Schematic: https://www.dropbox.com/s/mol...


Tariel Kapanadze - Radiant Energy from earth [2009]

Started by gabydewilde in sci.electronics.design13 years ago 3 replies

Tariel Kapanadze[1], has invented a multi kilowatt free energy generator. Several different implementations are shown[2][3][4] In one such...

Tariel Kapanadze[1], has invented a multi kilowatt free energy generator. Several different implementations are shown[2][3][4] In one such contraption the components include a radiator buried in the ground, a wire to a water pipe, a Tesla coil/joule thief, a spark gap, transformer, capacitors, 5 ferrite cores from old TV HV transformers, and some other unidentified components.[4] On July...


Oscillating regulators with ceramic caps

Started by Chris Jones in sci.electronics.design8 years ago 24 replies

I've just built up a batch of PCBs with several LM317 and LM337 regulators on them. As this thing will be in a hot environment, I wanted to...

I've just built up a batch of PCBs with several LM317 and LM337 regulators on them. As this thing will be in a hot environment, I wanted to avoid electrolytics so I used 10uF MLCC ceramic capacitors on the inputs and outputs of the regulators. Now that I have built it, all of the regulators oscillate! I had thought that it was only LDOs (with the drain or collector of the pass device ...


Surge Pulse Clamping with Ceramic Capacitors

Started by Klaus Kragelund in sci.electronics.design9 years ago 40 replies

Hi For an application I need to protect the electronics of an RS485 interface from surges (8/20us 1kV pulse) The normal way be to use a...

Hi For an application I need to protect the electronics of an RS485 interface from surges (8/20us 1kV pulse) The normal way be to use a transzorb, in a SMA housing or even a SOT23 device. That is not possible since we have to be able to withstand up to 30V DC on the bus also (that is handled by a special RS485 IC) The problem is that the selected breakdown voltage of the transzorb ...


Capacitance value for PIC crystal

Started by P E Schoen in sci.electronics.design9 years ago 41 replies

For most of my projects I use either a 14.7456 MHz crystal (57600*256) = or=20 20.000 MHz (for USB 96 MHz 24*f/5). The 20 MHz crystal I am using...

For most of my projects I use either a 14.7456 MHz crystal (57600*256) = or=20 20.000 MHz (for USB 96 MHz 24*f/5). The 20 MHz crystal I am using = specifies=20 a 20 pF parallel load, but my boards have 12 pF capacitors. I just = noticed=20 this and I think the value had been selected for a previous brand of=20 crystal, but the oscillator frequencies measure pretty close to the = ideal=20 ...


another LT Spice question

Started by John Larkin in sci.electronics.design9 years ago 35 replies

I have this circuit driving a pulsed laser. I want to compute the energy dumped into the laser and the energy stored in the power...

I have this circuit driving a pulsed laser. I want to compute the energy dumped into the laser and the energy stored in the power supply capacitors. The ballpark is 120 amps into a 20 volt laser for a few hundred microseconds. What I did was create a "B" behavioral current source whose equation is I = V(LASER) * I(LASER) which represents power, and dump that into a 1 farad cap. The...


Electronic components aging

Started by Piotr Wyderski in sci.electronics.design9 years ago 86 replies

Speaking of high reliability... I think that it is often a somewhat neglected issue, so I start this thread as a mean to collect *practical*...

Speaking of high reliability... I think that it is often a somewhat neglected issue, so I start this thread as a mean to collect *practical* observations for people who care about long MTBF. In other words, "if I had to build a device which should last 50 years, I would... what?" Resistors (if not overloaded): immortal Ceramic capacitors: as above Tantalum/nobium caps: ? Electrolytic...


LM317 compensation

Started by John Larkin in sci.electronics.design5 years ago 107 replies

LM317's like some ESR in their output capacitors. I don't want any electrolytic or tantalum caps in my new thing, just ceramics, and the sim...

LM317's like some ESR in their output capacitors. I don't want any electrolytic or tantalum caps in my new thing, just ceramics, and the sim sure rings: https://www.dropbox.com/s/11b3w42nsvpliki/317_nocomp.jpg?raw=1 But this fixes it: https://www.dropbox.com/s/9q80heyfbwh5frp/317_comp.jpg?raw=1 This ain't rocket science, but I haven't seen it done before. -- John Larkin ...


Do Electrolytic Capacitors FREEZE?

Started by Anonymous in sci.electronics.design4 years ago 24 replies

I have never known what the electrolyte is made from, inside of electrolytic capacitors. Is it a water based material, or oil based? If its...

I have never known what the electrolyte is made from, inside of electrolytic capacitors. Is it a water based material, or oil based? If its water based, it will likely freeze if left outdoors in cold weather. For example, your car radio has caps, and if it's parked outdoors in the winter, the caps in it will freeze. Yet, I have never found my car radio working poorly in cold weather. This ma...


Power supply design - does anyone know the transfer function?

Started by Anonymous in sci.electronics.design3 years ago

I have been designing (using)various Linear tech power supply chips. It seems current mode is the way to go. You can use their simulation tools....

I have been designing (using)various Linear tech power supply chips. It seems current mode is the way to go. You can use their simulation tools. It seems that the whole control of the whole power supply boils down to one external pin with two capacitors and a resistor that you attach to it. You pretty much start off with what their data sheet gives you , then use their simulatio


When to toss unused old electrolytic capacitors

Started by Anonymous in sci.electronics.design3 years ago 12 replies

I'm tidying up my home lab and getting back into it after a lapse of several years. I have unused electrolytic capacitors going back anywhere...

I'm tidying up my home lab and getting back into it after a lapse of several years. I have unused electrolytic capacitors going back anywhere from 10 to 30 years, stored in air conditioning. I understand that electrolytics can't be sold as new if they are more than 2 or 3 years old. At what age do they become unreliable and unsuitable for breadboarding and repair? I understand repair is th...


Breakdown voltage

Started by Anonymous in sci.electronics.design3 years ago 21 replies

I have set up simple circuit to test breakdown voltage: transformer + voltage doubler (with 22uF filterging capacitors) delivers about 156V. ...

I have set up simple circuit to test breakdown voltage: transformer + voltage doubler (with 22uF filterging capacitors) delivers about 156V. 156V goes trough 2.2M resistor to part under test. Paralel to the part is voltmeter. This seems to give reasonable results on most parts. However on some mosfets I see curious fenomenon: reading on voltmeter slowly increase and then stabilize at high...


RF board layout

Started by Pavel Margulis in sci.electronics.design2 years ago 10 replies

Hello, Experts I would like to ask for your opinion on following issue in RF PCB layout. I am dealing with a layout of RF PCB. There are...

Hello, Experts I would like to ask for your opinion on following issue in RF PCB layout. I am dealing with a layout of RF PCB. There are different components in the schematic, all are in SMT packages - fully internally matched to 50 Ohm amplifiers, bias-T, AC coupling 0402 capacitors, fixed attenuators, programmable attenuators, filters, RF switches. All components are declared in their