Generating this negative pulse?

Started by Terry Pinnell in sci.electronics.basics3 years ago 15 replies

I have a couple of simple 555 monostables, the first to delay the triggering of the...

I have a couple of simple 555 monostables, the first to delay the triggering of the second. https://www.dropbox.com/s/6uboy3fgd0ixhxa/GenerateNegPulse-1.jpg?raw=1 But I'm struggling to extract the brief -ve pulse required for the Main mono. I thought it would prove simple. But bread-boarding various combinations of R, C, diode and NPN or PNP transistor has so far not yielded a winning comb...


White Noise Source

Started by Chiron in sci.electronics.basics10 years ago 72 replies

I need a source of white noise (audio). It doesn't have to be perfect. I seem to recall that you could use a zener diode as a white noise...

I need a source of white noise (audio). It doesn't have to be perfect. I seem to recall that you could use a zener diode as a white noise source. Is this true? Are there any other possibilities? I anticipate using a 9-V battery for my power, and a few transistors to amplify the signal to drive earphones. You may ask, "why the heck would he want to do that?" Good question: http:...


Why dont they make a "Light Emitting TRIODE"

Started by Anonymous in sci.electronics.basics7 years ago 14 replies

The LED ("Light Emitting DIODE") is common place now. In fact it seems like they went from being simple "power on" indicator lamps to...

The LED ("Light Emitting DIODE") is common place now. In fact it seems like they went from being simple "power on" indicator lamps to the lighting of the future for darn near everything. But what I dont understand is why they have never made a "Light Emitting TRIODE"? (LET). It seems there would be many advantages!


cmos IC question

Started by default in sci.electronics.basics3 years ago 18 replies

I'm using some cmos IC gates in a project. All seem to have an internal protection network to insure that the inputs can't exceed supply or go...

I'm using some cmos IC gates in a project. All seem to have an internal protection network to insure that the inputs can't exceed supply or go more negative than ground with internal diodes. My question has to do with those protection diode ratings. How much current can they clamp to prevent exceeding the input voltage rating? For instance, I'm running one part of the circuit at 8 volts...


Battery parallel connection ?

Started by mowhoong in sci.electronics.basics9 years ago 2 replies

Parallel connection on lantern batterys will have higher current, but it wi= ll cause self dicharge to other battery with lower voltage. My...

Parallel connection on lantern batterys will have higher current, but it wi= ll cause self dicharge to other battery with lower voltage. My solution to = solve this problem was to add one diode to each battery, but I do not know = why this method was not used on commerical battery pad ? Can any members of= this group give me me advice. Thank you and happy x'mas to all members. Regards


Class D audio, and motor speed control

Started by Anonymous in sci.electronics.basics7 years ago 4 replies

I found this tutorial on Class D audio circuits: http://www.irf.com/product-info/audio/classdtutorial606.pdf and noticed there is no...

I found this tutorial on Class D audio circuits: http://www.irf.com/product-info/audio/classdtutorial606.pdf and noticed there is no freewheeling diode, as there is in motor control circuits. Why is this? Thanks, Michael


Weight of electronic equipment

Started by Veek M in sci.electronics.basics6 years ago 22 replies

I'm importing some electronic parts/equipment (1kg worth) and wanted to compute a reasonable estimate of shipping costs - could someone weigh...

I'm importing some electronic parts/equipment (1kg worth) and wanted to compute a reasonable estimate of shipping costs - could someone weigh their parts and post the values. What are the weights of various types of: Through-hole components: diode, capacitor, inductors, transistor, ICs, crystal, LED, ferrite cores-beads, Potentiometers, Trimpots, Photodiodes/IR, microprocessors, ...


MCU reset during relay switches ON

Started by Niresh in sci.electronics.basics1 year ago 7 replies

Hi, Could any please suggest how to avoid MCU reset with voltage glitches/noise during relay switches ON. I have protected the relay coil with...

Hi, Could any please suggest how to avoid MCU reset with voltage glitches/noise during relay switches ON. I have protected the relay coil with free wheeling diode and MCU with 2x10uF parallel with 100nF near VDD of MCU and 1uF across RESET pin. Regards, NiK


Is this homemade battery charger circuit dangerous?

Started by Kanon Kubose in sci.electronics.basics9 years ago 41 replies

The other day I found plans for a $3 battery charger that was just a diode = and light bulb in series with the battery, using mains electricity....

The other day I found plans for a $3 battery charger that was just a diode = and light bulb in series with the battery, using mains electricity. I poste= d a question about modifying it with a dimmer switch here: https://groups.g= oogle.com/forum/#!topic/sci.electronics.design/dW8otaIKNyE Everyone there said I was a candidate for a darwin award and that I should = come to sci.electronics.ba...


Confirmation needed

Started by Bob Engelhardt in sci.electronics.basics5 months ago 5 replies

I'm going to make a 12v DC power supply with a linear reg. I will half-wave rectify 12v AC and have a smoothing cap. The load is only...

I'm going to make a 12v DC power supply with a linear reg. I will half-wave rectify 12v AC and have a smoothing cap. The load is only 10ma. So: 12v RMS is 17v peak, minus the diode drop of 0.7 is 16.3v peak. Using a 47uF cap, the ripple will be 3.5v p-p. So the min voltage into the regulator will be 16.3-3.5 = 12.8. Ripple calculated from Vpp = i/fC (.010/(60*47e-6). Am I missing ...


Which diode is faster ?

Started by Anonymous in sci.electronics.basics9 years ago 2 replies

Hi, http://www.digikey.com/product-detail/en/MBR40250TG/MBR40250TGOS-ND/1477185 OR...

Hi, http://www.digikey.com/product-detail/en/MBR40250TG/MBR40250TGOS-ND/1477185 OR http://www.digikey.com/product-detail/en/UF4002-E3%2F54/UF4002-E3%2F54GICT-ND/3025933 Thanks jess


Baffling simple circuit

Started by Bob Engelhardt in sci.electronics.basics4 years ago 15 replies

https://i.imgur.com/OWbZIrH.jpg The circuit monitors a battery & when its voltage is above an adjustable threshold, it closes a relay. When...

https://i.imgur.com/OWbZIrH.jpg The circuit monitors a battery & when its voltage is above an adjustable threshold, it closes a relay. When the voltage drops below the threshold, it turns off and latches off (the feedback diode). What's baffling is that it works for a second or 2 and turns off. Particularly baffling is when I measure the voltage at the arrow, it stays on. The voltm...


Automotive relay question

Started by DaveC in sci.electronics.basics7 years ago 15 replies

I have a 12V SPST cube relay in my junque box. The diagram molded into the relay?s housing includes a component connected in parallel with the...

I have a 12V SPST cube relay in my junque box. The diagram molded into the relay?s housing includes a component connected in parallel with the coil which looks suspiciously like a resistor. It?s not a back-emf diode: I connected the relay coil using both polarities (using a current-limited power supply) and the same current draw is measured. What is the purpose of this resistor? ...


Automotive relay question

Started by DaveC in sci.electronics.basics7 years ago 2 replies

I have a 12V SPST cube relay in my junque box. The diagram molded into the relay?s housing includes a component connected in parallel with the...

I have a 12V SPST cube relay in my junque box. The diagram molded into the relay?s housing includes a component connected in parallel with the coil which looks suspiciously like a resistor. It?s not a back-emf diode: I connected the relay coil using both polarities (using a current-limited power supply) and the same current draw is measured. What is the purpose of this resistor? ...


Developing a Circuit Simulator from Scratch

Started by Anonymous in sci.electronics.basics15 years ago 19 replies

Hi, Can anyone give me some directions on how to develop a circuit simulator from scratch. I need to develop a simple spice...

Hi, Can anyone give me some directions on how to develop a circuit simulator from scratch. I need to develop a simple spice compatible simulator,that can read in spice netlists. I will be using C++ to code the simulator. I need to support only simple R,L,C, diode and mosfet devices and DC,AC and transient analyses. I would be using the Ebbers - Moll models. The problem is that I could not ...


Automotive alternator windings & rectifier

Started by Mike Cook in sci.electronics.basics8 years ago 1 reply

http://www.autoshop101.com/forms/alt_bwoh.pdf has photos of an alternator with 4 connections for windings (each of 3 phases + common), and...

http://www.autoshop101.com/forms/alt_bwoh.pdf has photos of an alternator with 4 connections for windings (each of 3 phases + common), and the 8 diode rectifier. But wiring diagrams show only 3 connections and 6 diodes. Where does the common winding terminal connect (there is a connection on the rectifier plate)? Where do the other 2 diodes connect? I handled one of these disassemb...


Automotive alternator windings & rectifier

Started by Mike Cook in sci.electronics.basics8 years ago 28 replies

http://www.autoshop101.com/forms/alt_bwoh.pdf has photos of an alternator with 4 connections for windings (each of 3 phases + common), and...

http://www.autoshop101.com/forms/alt_bwoh.pdf has photos of an alternator with 4 connections for windings (each of 3 phases + common), and the 8 diode rectifier. But wiring diagrams show only 3 connections and 6 diodes. Where does the common winding terminal connect (there is a connection on the rectifier plate)? Where do the other 2 diodes connect? I handled one of these disassemb...


Protection for CMOS output?

Started by Pimpom in sci.electronics.basics8 years ago 2 replies

I want to build a simple manual count-up system with a local as well as a remote 2-digit display. The system will be based on discrete CD4xxx...

I want to build a simple manual count-up system with a local as well as a remote 2-digit display. The system will be based on discrete CD4xxx CMOS logic and the count pulses will be sent to the remote unit along with a 12V supply over a shielded 2-core coax cable. The cable is ~20m long. The remote input will have the usual schottky diode plus resistor protection. The output from the ...


Re: DTL (diode AND gate)

Started by Tim Wescott in sci.electronics.basics6 years ago

On Fri, 26 Feb 2016 16:57:18 -0800, George Herold wrote: > On Friday, February 26, 2016 at 5:05:33 PM UTC-5, Tim Wescott wrote: > > On Fri,...

On Fri, 26 Feb 2016 16:57:18 -0800, George Herold wrote: > On Friday, February 26, 2016 at 5:05:33 PM UTC-5, Tim Wescott wrote: > > On Fri, 26 Feb 2016 07:47:46 -0800, George Herold wrote: > > > > > Hi all, Another digital question. > > > I'm doing this pulse thing. Pulse widths were, > > > 1,2,4,8,16.. simple set by a rotary switch pulling one bit high. > > > > > > The boss wanted a finer d


Re: DTL (diode AND gate)

Started by George Herold in sci.electronics.basics6 years ago

On Saturday, February 27, 2016 at 11:51:38 AM UTC-5, Tim Wescott wrote: > On Fri, 26 Feb 2016 16:57:18 -0800, George Herold wrote: > > > ...

On Saturday, February 27, 2016 at 11:51:38 AM UTC-5, Tim Wescott wrote: > On Fri, 26 Feb 2016 16:57:18 -0800, George Herold wrote: > > > On Friday, February 26, 2016 at 5:05:33 PM UTC-5, Tim Wescott wrote: > > > On Fri, 26 Feb 2016 07:47:46 -0800, George Herold wrote: > > > > > > > Hi all, Another digital question. > > > > I'm doing this pulse thing. Pulse widths were, > > > > 1,2,4,8,16.. s