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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...

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...

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)\$.

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.

hi can make tone control circuit on arduino using lm386 , if not other ic used please me out? tone control circuit in audio system variable filter. it's used boost frequencies, attenuate other frequencies , let others is. purposes of such filtering: creative sound modifying (=adjustments subjectively result) compensating uneven frequency response of equipment , room, based on mesurements today high quality complex filtering possible in digital domain. signals ad-converted , filtering made calculations. arduino unfortunately slow , has low resolution ad conversion serious real time digital audio signal processing. if search "dsp arduino", audio examples @ best music or other sounds played through old-fashioned analog long distance phone line. thus arduino digital audio signal processor isn't serious option - except if have signal stored digital data , allow @ 10...100 times longer processing time duration of signal. in case use pc , excel or matla...

i have no experience of dealing pcb manufacturers except time once used pcbway's service. know if there standard pcb board sizes 1 needs create when getting custom pcb made? my basic idea not incur cost loss of material pcb manufacturer faces. example, let's use board of 10*10 inch manufacture , submit custom board request dimension of 7*7 inch, increase cost of pcb? sometimes pcb makers have per-panel price. tell size using..or more importantly, area have work with-- usable area (not panel size) @ least 10" x 16", maybe 10.5" x 16.5" or bit more. small panel. large production believe larger panels more typical. typically phenolic single sided boards use larger panel sizes. this reference lists typical standard pcb panel sizes follows: panel borders (maybe 0.5" on each side) take away area. it not particularly important unless pcbs (or self-panelized pcbs) getting size few panel- materials not biggest part of pcb cost in prototype...

i'm trying make push-pull audio amplifier pair of power darlingtons (tip142 , tip147), i'm having problems biasing. here's diagram of 1 of configurations: here i'm using 3 diodes, used different things in place try correct biasing voltage. with biasing voltage lower 2.2 v (between bases of transistors) has crossover distortion, because there'll small parts of signal none conducting. with 2.2 v or more, both conducting , there's no more distortion, there's problem: current flowing between them escalates heat until take on fire (being starting current isn't great , they're on large heatsink, heatsink doesn't have time heat, fast happens). they're stable biasing voltages lower 2.1 v, there's distortion. the components heating here output transistors, i've cheked , none of resistors or diodes heating up. i've checked if negative feedback help, didn't, because voltage in output doesn't change current flowing t...