EE1000 Project 4 Digital Volt Meter

Transcription

1 Ovrviw EE1000 Projt 4 Diitl Volt Mtr In this projt, w mk vi tht n msur volts in th rn o 0 to 4 Volts with on iit o ury. Th input is n nlo volt n th output is sinl 7-smnt iit tht tlls us wht tht input s volt is to th nrst volt. Dsin Rll tht whn w r with sin prolm, w n to ollow ths sin stps: 1. Unrstn th onpt. 2. Unrstn or rt n lorithm to o th jo W ll isuss this, low. 3. I th prolm is too omplit, suivi n rpt, othrwis, sin it. 4. Tst. Approh (Alorithm) On wy to mk (implmnt) this projt is: 1. Convrt th nlo sinl to iitl. 2. Convrt th iitl t into inry t. 3. Do th inry t or th 7-smnt isply. This lorithm n illustrt y lok irm (S Fiur 1). Anlo Input Convrt to Diitl Convrt to Binry 7-Smnt Dor 7-Smnt Disply Fiur 1 Blok Dirm Rll tht th rrows twn th loks rprsnt inormtion, not nssrily wirs. W will wnt to suivi this sin into 3 prts: () th iitl onvrsion, () th inry onvrsion n () th 7-smnt or n isply. Diitl Convrsion Th sist wy to onvrt n nlo sinl to iitl is to us omprtor. A omprtor tks two input volts (ll n -) n outputs hih iitl sinl i th () input hs hihr volt thn th (-) input, othrwis it outputs low sinl. W will n 4 omprtors to ompr th input to 0.5V, 1.5V, 2.5V n 3.5V s shown in Fiur 2. Th output o ths omprtors r iitl sinls w will ll C 0.5, C 1.5, C 2.5 n C 3.5 rsptivly.

2 V in 3.5V C V C V C V C 0.5 Fiur 2 Convrtin n Anlo Sinl to Diitl. For this projt, w will usin th MCP6544 qu omprtor (4 omprtors pr hip). A pin irm is inlu t th n o this oumnt. Bs on th input volt, Vin, th output sinls will rspon s shown in Fiur 3. Input Volt C 3.5 C 2.5 C 1.5 C <V in < <V in < <V in < <V in < <V in Fiur 3 Comprtor Outputs Bs on Input Volt All tht rmins is to nrt th ix input volts (0.5V throuh 3.5V). Th sist wy to o this is y mns o Volt Divir. A volt ivir is simply nk o sris rsistors sin to prou on or mor spii volts. Sin w hv rult 5 Volt supply, w will us tht or th Volt Divir s shown in Fiur 4. V (5V) 3KΩ 1KΩ 3.5V 2.5V 1.5V 0.5V Fiur 4 Volt Divir

3 Th rul or th volt ivir is tht th rtio o rsistor to th totl rsistn quls th rtio o th volt ross tht rsistor to th supply volt. In othr wors, V = R V R In this s, V totl = 5V n R totl = 10K. I you work out th mth, th volt ross th 1KΩ rsistor is 0.5V, th volt ross h rsistor is 1.0V n th volt ross th 3KΩ rsistor is 1.5V. Ths volt rops iv us th vrious ix volts w n or th omprtors. Noti tht th rsistor vlus n sl y ny tor (.. oul or hlv) without tin th volts tht r prou. Convrsion to Binry Sin th volts w wish to isply r in th rn 0-4, it will nssry or us to us 3-it sinl to rprsnt th volt. W will ll thos its B 2, B 1 n B 0, with B 0 in lst siniint (i.. th 1 s it). Th inry sinl ns to nrt s on th inputs C 0.5, C 1.5, C 2.5 n C 3.5 s shown in Fiur 5. C 3.5 C 2.5 C 1.5 C 0.5 B 2 B 1 B 0 Disply Fiur 5 Comprtor Outputs Bs on Input Volt Th simplii loi qutions or th 3-it inry sinls r: B = C. C. C. C. B = C. C. B = C. You will n to sin loi iruit (muh s you i in Projt 1) to implmnt ths qutions. Your inputs n outputs r tiv hih. (I tiv low inputs r sir, you n xhn th n inputs in Fiur 2.) 7-Smnt Dor n Disply Doin inry t or 7-smnt isplys is muh lik oin inry t or th i pips in Projt 1, n w n rtinly o h o th smnts with NAND n NOR ts, ut ortuntly n intrt iruit (IC) is vill tht n o ll 7 smnts t on. Th prt numr or tht IC is 74LS47. Th 74LS47 tks 4-it inry numr s input. (Sin w hv only 3 its, w will n to onnt th 4 th input to roun.). It lso hs rippl lnkin input

4 (RBI) n LED tst (LT) inputs, oth o whih must hih (.. onnt to V) or th vi to untion proprly. Th 74LS47 hs svn outputs ll -, ll tiv low, to riv th svn smnts o th isply. A typil iruit usin th 74LS47 is shown in Fiur 6. Pin irms or th 74LS74 n th isply r vill t th n o this oumnt. B 3 B 2 B 1 B 0 D C B A 74LS47 220Ω V Tstin Fiur 5 7-Smnt Dor n Disply Us on hnnl o th powr supply to provi powr to your iruit throuh th 5V rultor. Connt nothr powr supply to V in. B vry rul not to riv V in ovr 5 Volts or unr 0 Volts, s this my m th omprtor. Vry th volt on Vin rom 0 to 4V n vriy tht th isply shows th volt (to th nrst volt). Not tht minor rrors n our us th rsistors you us to mk th volt ivir hv tolrn o 5%.

5 Pin Dirms MCP LS47 SA56-11SRWA