SFH900

SFH900 SIEMENS | Alldatasheet

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| SIEMENS CAPITAL/ OPTO T- 4(-O2 jo D | 6236326 00035649 T _ SIEMENS i Whether for an industrial plant or a hobbyists’ drilling machine, an electric drive will hardly be acceptable nowadays without speed control. Incremental bar patterns simply applied to rotating shafts can be detected by the new Siemens reflex optical sensor, the SFH 900. The information can be processed with a minimum of circuitry, whether for a high rate of black-to-white transitions or just single, slow transitions. Construction The SFH 900 optical sensor is a remarkable component | F79," .,,Sft 200 reflex optical sensor. front anc back even by virtue of its shape alone. Its maximum height of " 2.2 mmis in the trend of today's electronics, of putting a large number of functions into a very small space. The | small dimensions allow it to be used where ordinary | optical sensors run into space or other problems. Fig.1 is : an enlarged picture of the device. Dimensions and pin } configuration are shown in Fig. 2. Fabricated by lead frame technique in a thermoplastic “ package, the sensor uses a GaAs infra-red diode as a 7 : radiation emitter and a large-area phototransistor as the detector. High sensitivity is ensured by a 1 mm? radiation sensitive area and a current gain of almost 1000. The ! effect of unwanted ambient light is almost screened out : bya filter. ‘wo fixing notches are a help in mounting the device. : Lead frame technology accurately locates the optically | active areas relative to these notches and thus to the component body. Fig.3 is an example of one form of mounting. Fig.2 Outline dimensions and pin connections of SFH 800 Radaton sensine Pa comnectons » wees | 1 3 or ig . gy 8! eg — x fis zt 33 gis se rrp alt Pa 2

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STENENS CAPITAL/ OPTO T-4/ -03 30» WY s236324 0003570 a Characteristics | Main technical data are given in the Table. Turn-on and | Fig.4 SFH 900 collector current Jo as a function of . turn-off times are also important. These depend essen- | forward current is wih GO% cffuse rellectin at clstance tially on the collector current J and the load resistance R.. Typical switching times for Jc = 1 mA and R, = 1k are 60 to 70 ys. he 10 The user will be mainly concerned with the following { Ly [TT tty points: « What collector current, Jc, can be expected under ow TTT TAT given static conditions? tT TAT « What are the signal amplitudes when scanning bar rr fTrfteeyrt yy patterns of different pitches? + What is the temperature dependence of the collector LTT TY TT current and what is the repeatability of the measured a-L PI Tr values? LAT Tt Collector current LE Ty } Dependence of collector current on emitter diode forward rI7_ET Try 4 current /- is almost linear at forward currents above bol p72 10.mA, as can be seen from Fig. 4. At currents below 11m the dependency shows aimost a square fw, The Zee : measurement was made with a standard reflector (Kodak Y neutral white test card, r= 90%) at a distance of 1 mm. om(T TET TTT Fig.8 shows [c characteristics for distances of 0.2 to 10mm at a constant forward current of 10mA. The rr curves are for four different reflecting materials: two U,=5v standard Kodak reflectors with 15% and 90% reflection, polished aluminium and a strongly absorbing foil. DC-fix adhesive tapes and other tapes commonly used for printed circuit layouts proved particularly suitable. It should be mentioned that the curve for polished alu- minium in Fig.5 is very similar to the Kodak reflector response with r= 90%, in spite of the reflection being , si Fig.6 SFH 900 collector current /, as a function of mirrored by the metal’ and diffused by the standard reflector, asa result of the wide directional characteristics | “#etor distance d with ciferent reflector materials of the emitter and detector. k At short distances (e. g. d= 0.25 mrn) very large changes of current per unit distance are obtained, Because of D> tector these steep edges, which can only be used dynamically, CSRs TN eal the SFH 960 may also be utilized as a microphone. V7 au fl H Fig.3 Suggestion for mounting the SFH 900. OC i Projections N in the flexible plastic clamp locate in { a | corresponding notches in the body of the optical sensor 1 ff rerisk 20%} \\ | “ie V/\\ \\! GS a aa | BAEANG : w ELEN N on 1 mm 10 : + ; Forward current Jp = 10 mA H Operating voltage Us = 5 V. j . | 11-60 i

“SIEMENS CAPITAL/ OPTO T- 4-03 qo oD I 6236326 0003571 4 Emitter (GaAs infra-red diode) Reverse voltage Un 6 v Forward de current Te 50 mA ‘Surge current (t = 10 ys) fesm 15 A Power dissipation (Tan = 40°C) Pra 80 mw ‘Thermal resistance Rosy 750 KW : Detector (silicon phototransistor) Collector-emitter voltage Uceo 30 v Emitter-collector voltage Veco 7 v Collector current Ig 10 mA Total power dissipation (Tyr = 40°C) Pes 100 mW Collector-emitter leakage current (Uce = 10 V) Teco 20 (= 200) nA Photocurrent under ambient light (Uce = 6 V) (Ee = 0.6 mW/cm?) Ip s3 mA Reflex optical sensor Storage temperature range Ts 4010485 °C Ambient temperature range Ty 40 to +85 °C Junction temperature qT 100 °C Total power dissipation (Tay = 40°C) Bat 460 mW : Collector current ‘SFH 900-1 Tee 203 m , Ap =10 mA; Uce= 8 Vide t mm) ____ SPH 900-2 eg OG mA Table Selective characteristics of SFH 900 Resolution of black-and-white patterns : : As can be seen from Fig. 5, strongly reflecting and badly sector current when . teflecting materials give collector currents differing by a Fa ni tiaereante pater collector current wi | factor of about 25. Strongly reflecting means »whites, 1 badly reflecting »black«. : If a black-to-white transition is scanned, the displace- k 100 : ment distance between the »fully white« signal and the (eo) % [| |Z r [| »fully blacks signal is 4 to 5 mm (Fig. 6). al Z| If, in contrast, a regular bar pattern is scanned, the signal t me, amplitude becomes smaller the smaller the bar width. el Fig.7 shows clearly how the excursion is affected: the | 7 maximum white signal becomes smaller with decreasing a bar width, while the minimum black signal becomes VI is | larger. Fig. 8 shows the signal exoursion itself, to make it nt clearer. Here a regular pattern and a single white bar are a compared. The excursion is referred to a single black-to- q SL white transition corresponding to a 100% signal ex- rr rr or) cursion. —+> Barwidth | A bar width of 3mm can thus be detected without : significant loss of sensitivity. The signal excursion, how- ‘ ! ever, drops to as low as 10% using a grid of 1 mm bar : Fig.6 Resolution of a black-to-white transition, Relative Fig.8 Relative signal excursion as a function of white | collector current as a function of sensor position s bar width de 100 SS Ip=10 mA, d= 1 mm | “TS i

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(el) Y | i. J _| , a] LTV t Y\\ | | | | {ji 60) i Ne | PAT | a 0—77 aS wT | | NU ila a V4 TI li : _ = ‘ Reflector distance d= 1mm 1 2 3 4 San6 = | Emitter diode current /p = 10 mA ——> Barwidth . 11-61

SIEMENS CAPITAL/ OPTO T-9/-03 0 > Wasaaae, oonasza + width. An apparently higher signal excursion is obtained! when a single 1mm wide white bar on a black back- | Fig.9 Relative collector current as a function of ground is scanned. The result is then about a 30%, as | temperature shown in Fig.8. The optical sensor can be used for scanning in any 7 position, regardless of whether the emitter-detector axis Le 120 i is at right-angles to the scanning direction. Tests have (alg : shown that the device sensitivity is independent of i ————— i direction. If a white spot on a black background (or vice- oF — . i versa) is to be detected without loss of sensitivity, this H should have a minimum area of 5x5 mm. From this we 0) can conclude that a pattern bar must not be larger than 5mm. [ Thus the resolution capability of the SFH 900 seems to fof ot 4 | be limited to bar widths of 1 to 2 mm minimum. In fact, 0 however, considerably higher resolutions can be ob- tained when gratings are used. An example is given vere aT TE | ‘Temperature dependence f) The temperature dependence of the output signal is 6 0 % = CS shown in Fig.9. This fortunately very small dependence —e results from the combination of the temperature depen- U,=5V d= 1mm dent diode emission (approx. -0.55%/K) with the tem- Ie= 10mA r= 90% perature dependent current gain of the phototransistor | © —— typical response (approx. +0.9%/K). As these two parameters partly | -~-~ spread of characteristics compensate for each other the temperature dependence | (including long-term effects) ! of the output signal is fairly small. : ‘There is a spread of characteristics in the different devices but they remain within the specified tolerance range, allowing for ageing, with a probability of at least 95%. 2 mA. Signal processing and triac triggering are done by the new TLB 3101 phase control IC. Total current needed for control is around 7 mA, including the SFH 900. : Applications Pulses from the optical sensor are first amplified, then converted by a monostable to constant pulse width and Speed control for de motors finally filtered to give a mean value, By comparison with a Asimple speed regulator circuit for small dc motors can sawtooth voltage the gate trigger time for the triac is be designed using the TCA955 device. Fig.10 is an fixed. A soft start is given by transistor T1. example. The teeth of a toothed wheel on the motor shaft The range of speed regulation is 5000 to 16000 rpm. The i | serve as reflectors (40 teeth on a wheel of approx.60 mm _ reflector is a disc mounted on the motor shaft, and at its ! diameter). Pulses from the optical sensor are converted periphery this disc has, as an example, 6 pairs of black by the TCA 965 into @ de voltage proportional to speed. and white segments. The pulse signal is first amplified, then frequency dou- H bled, then fed to a monostable which produces a square Shaft encoder with direction sensing wave with a constant pulse duration determined by the This example shows how gratings can be used to give a A, C; product. The mean value of this pulse train is considerable increase in resolution. A transparent disc of determined by capacitor C2 and an 8.7 kQ internal about 130 mm diameter has an array of 200 opaque bars resistor. at its periphery (Fig. 12a). The bar width is thus about ' The voltage present at C2, still with a slight triangular 1mm. A second grating with reflecting white bars Is modulation, is compared with an internal set value. The placed under the disc. If the disc pattern and the grating difference Is amplified and determines the duty cycle in beneath are set gap to gap, the detector »sees« 100% the subsequent mark-to-space ratio converter. The black. If the bars of the two gratings are on top of each motor is connected to the operating voltage via a BD 675 _ other the image appears as 60% white. So, when the disc switching stage, which runs to the rhythm of the duty _ is rotating the useful amplitude is therefore about 50% of | cycle. A larger mark-to-space ratio causes the speed tothe full black-to-white excursion. | increase. The desired frequency can be set by Pi overa The grating pattern is constructed so that one half is wide range. displaced by 90° of a grid period with respect to the other half. If @ reflex optical sensor is assigned to each half, on t Speed control for ac motors rotation of the disc the output signals will be roughly : This is mainly intended for use in the consumer field, in sinusoidal and displaced by 90° from each other. This : such things as kitchen appliances and drilling machines. means that patterns of half bar width can be successfully : {tis important that the speed indicator should have a very resolved. | . low current consumption as it is supplied from a simple in further processing both sinewave voltages are con- | line rectifier circuit using a series resistor. The specimen verted into square waveforms, also phase-shifted by 90° circuit in Fig.11 has an emitter diode current of only (Fig. 13). 11-62 |

SIEMENS CAPITAL/ OPTO T -4/-03 jo (OD I 4236326 0003573 1 r Fig.10 Speed regulator using SFH 900 reflex optical sensor and TCA 955 integrated speed control I 1w efector 15 nF OF _ Atootbed wheed Set frequency PA} nore) p 500 10K Hoo} [] x2 iss at af Tuy ww Ts : EAE 16 — +o 67s|

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totoJ ' eis See : Anes Cr OnE Fig.11 Speed regulator for an ac motor using SFH 900 and TLB 3101 [] 2x0 [] 1002 Aes uf] [] 20v S3uF tt 22 00 100k 12 anof] Ho — a i oF Bayer oz2yF — sheton ZR gave! fi " fae ae ri 3 v7 180 |0 lt ET | Lt f> | Le fs a Pade || = s{ | : ; =] a ak i iforo) [] 102 Us Aa Pd is sa @ ‘800 d 470] 180 1 : fy soi [see hi = Y eave? wees x : 11-63

SIEMENS CAPITAL/ OPTO T- - 90 6D 6236326 GOOS574 3 | The rising edge of on square-wave (signal 1) is used for counting. It triggers a monoflop which generates @ | Fig.12 Waveforms showing the operation of a shatt pulse of short duration relative to the square-wave | encoder with direction sensing period. The other, 90° shifted, square-wave controls the direction of the counter (Low = forward, High = back- Mean ward). white | According to the direction command, the conditions in level ! Fig. 13 come into effect. The active clock edge coincides () ! with either the low level or the high level of signal a an : 2. Counting therefore takes place in accordance with —\\f~ 5 ue | forward or backward rotation of the shaft. Fig. 14 gives p42 ! the detailed circuit diagram of the shaft encoder. ! i ; ‘The counter used has a range of two decades and gives boty 0 gupit the BCD separately for each digit. ZNZ 8 feet A 7-segment decoder-driver follows this for-each of the WZ.--NiZ---- 9 two LED displays. The number of digits can be increased | Hl by cascading several stages. i { For the purposes of explanation any bar in the pattern can be considered as the starting point and the counter ~~ stor | reset to zero using the reset key. If now the disc is turned 1 po a | at any speed in either direction with respect to the pore dot ! stationary mark, the counter indicates the bar number er i difference with respect to the starting point. As only do LTE T ET 1 compactor : voltage coupling is used the rotational speed may have P LED | (conor : any arbitrary minimum value. T ot FE Counting Pot fb die it T atput H . { | monosabi : 1 {caning . | 1 deecten) p> monostable io 5 Fig.12 Example of a patterned disc (a) and its counting ' arid (b) { ' a | omy, | S\\ 2 NS A BS Z SS Z = 2 | Z Ss Z S eZ S NY, sy a Ul \\S % “QU . 11-64

SIEMENS CAPITAL/ OPTO T-4/-03 10 > a2aab32b 0003575 ae : Fig.14 SFH 900: circuit for shaft encoder with direction sensing | [a Hina U H [na EINE] | aE rel_84fts.t0.15 16 poo pores . y 990 [Jone | 47D | casos [ea | musa7 E Bi oe hs] ” Lael [2 4 3 o>. 7 [a2] muse} —4 lpa tem fp |) food Bs Ky [Jt ecntes 7 3 4] uF = i +5v8 +5V8 D | = Be . 11-65