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i attempted make myself 2-in-1 programmer can program both at89cx051 , at89s52 on same board without having plugging/unplugging of port. the main issue strobe pin aka reset (rst in circuit). (pin 1 of db25 connector). tested pc , got no results. what seems work if connected rst vcc via 1k resistor. works because though output @ 3.8v instead of 5 (which vcc at), puts at89s52 in reset mode expected, i'm not getting 12v @ pin 1 of small at89cx051 socket. if don't make manual connection, 1.4v measured @ rst, after added 10k resistor between vcc , rst. without rst being forced ground, should 5v i'm not. i have tested transistors manually leg leg using diode setting on multimeter , turned out fine. resistors going base of transistors 2.2k , used 1k resistors in place of diodes. other resistors 10k. resistor going buffer (74hc125) 0 ohm. all capacitors 0.1uf. why getting such awkward voltages reset pin? using weak of resistors or something? update so ended ma...

hello have cheap ftdi going recreate on pcb can flash atmega2560 chip onboard, ftdi has dtr line pulled low when sequence starts stays low instead of going low high after 1ms 50ms, need find out how create simple circuit when pulled low goes high, how can this, have simple components hand. my stocked parts: 103 ceramic caps 25uf aluminium caps 220uf aluminium caps some blue ceramic caps labeled "10" practically common resistors values 5v zener diodes 5v switching diodes npn transistors n channel mosfets 5v reflecting diodes can make using ? else can what's needed. many thank edwin sorry it's atmel atmega 2560 chip on pcb have serial lines , reset,5v,ground , 2 gpios on pin out. can flash ftdi. , ftdi dtr line stay low , need pluse rest line need figure out how use low signal pull reset low high right after. if try on arduino mega or uno holding down reset not work it's pulse going low high load boot manager. hence dfti dtr...

i know in magnitude spectrum of single square dc pulse (0-8v) lobes 0 @ frequencies $$\frac{1}{t},\frac{2}{t},\frac{3}{t},...etc. $$ t=pulse duration. if square pulse goes -2v 6v, formula 0 points of spectrum still same, ie. $$\frac{n}{t}$$ n=1,2,3... etc. , t=pulse duration? what difference? applying offset signal change spectrum @ dc (frequency of 0hz). if single square pulse goes 0v 8v, value of dc \$\mathcal{f}\{ f(t)\}|_{\omega=0}=0\$. if square wave goes -2v 6v, \$\mathcal{f}\{f(t)\}|_{\omega=0}=-2\cdot\delta(0)\$.

below want select , edit bottom wire of 3 parallel wires: but when click on bottom wire program selects middle wire because share same net. is possible single out desired wire segment without selecting entire net in altium? yes you need use "break wire" feature first - split wire up. think it's in "edit" menu.

i'm trying find "same or better" equivalent replacement 747 opamp. footprint / pinout can different, don't mind. using parametric search on arrow, while reading datasheet 747 found lt1355 might replacement. however, quite expensive; $16.89 1 single ic (dip package). searching lt1355 on octopart shows arrow cheapest one, price steep me. i'm fine around $8/pc. what other dual opamps can serve replacement 747? usually asking products/parts off-topic since can benefit wants better 741, i'm making exception. there literally hundreds of suitable 741 replacement opamps. the parts list waaaay expensive. have special properties few designs need. you should not looking 741 replacement per sé more "generic opamp". there usable opamps had less money. lm358, 10 1 euro (shipping included!) on ebay other examples: mcp602, ca3140, tlc271 most of these have versions 1, 2 or 4 opamps in 1 housing. you have compare datasheets see suits ...

can sample , recover signals non infinite "length" using nyquist shannon theorem? example if have signal $$ x(t)= u(t+5)-u(t-5) $$ , know sampling period t less 10s (t<10). can recover using nyquist theorem? if not , recover it? edit: have taken fourier transform of signal , : $$x(ω)=2i(\frac{1}{iω}+πδ(ω))sin(5ω)$$ can lead finding period $$\frac{2π}{5} $$ , see if f>= 5/π can recovered. may not possible because used theorem although on finite signal no need think "finite length". though continuous time signals defined infinite time interval, in practice analyse in finite interval only. x(t) defined in interval [-5 5]. the frequency domain representation of such signal infinite bandwidth sinc function. hence not possible define particular sample rate per nyquist theorem, reconstruct without losing information. can sample definite sample rate, implicitly band limits signal. sampled signal after reconstruction through dac , lpf, not pe...

hello have transformer ebay north court 50 amplifier. there not information online. has 400 0 400 volt ht think ran pair of kt66 valves gz34 rectifier dimensions l x b x h 4" 3" 4" if can me out on 1 great the main determiner of transformer power rating material , cross-sectional area of core. sets power level @ core saturate, , manufacturers don't want use more steel absolutely have to. as rough estimate, since these transformers use same kind of steel laminations , same relative geometry, sufficient make judgement based on volume/mass of core. since core majority of total mass of transformer (the windings tiny fraction), weighing enough, why marko made comment.