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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 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...

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.

i have old audio amplifier (jvc a-gx2b) produces crackling noises on 1 of outputs. so, opened , discovered 2 largest capacitors seem leaking : can replace capacitor same characteristics (4700uf 50v), or should instead take specific capacitors audio? if yes, ones ? in addition, have interest replace capacitors of amp (not 2 largest)? 1: wear safety gloves when handling toxic leaky capacitors, remove , clean safely isoprop. , mark note polarity (-) 2 : measure dia , lead pitch dxl [mm] sort parts this 3: audio or better low esr, highest ripple current caps. < 50mohm, > 3aripple 4: better caps run cooler lower esr , rated higher temp. may not fit. 5: japanese caps have better reliability i suggest 1st choice panasonic @ digikey .. cost of shipping may more cost of caps. as suggested: cap voltage must same or more - capacitance tolerance doesn't matter, , may larger value. - large e-caps may replaced @ same time.

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 using tps61021 boost converter ic increase input voltage 1.2v 3.3v. have designed boost converter application called ti webench. input voltage: 1.2v output voltage: 3.3v min current: 300ma the pcb have designed, measuring 3.3v, efficiency pathetic. below 25%. in bom, ti webench software recommends using 10uf 10v capacitor, using 10uf 6.3v. not able understand why efficiency low? datasheet inductor . below in tabular format have written current values have measured multimeter. fig.1 measurement of current @ different load resistance. fig.2 ti webench application output fig.3 schematic design of boost converter pin = 1.2v × 570ma = 684 mw pout = 3.3v × 105 ma = 346.5 mw efficiency = pout/pin = 346.5/684 = 50.7% how on earth did come 18.42%? similarly, 64% , 70% other 2 loads. these numbers sound pretty me @ these voltages. did webench give efficiency estimates specific configuration?