DE2514167B2 - CONTROL CIRCUIT FOR QUASI-ANALOGUE LIGHT BAND DISPLAY - Google Patents

Description

! Γ i'i i.l i: 1 I '' -. '.'! U '. IUl IiIO

': ·. ■ lic .-. Us ι uicr analog

il ^1: Sl | ''|; llc .'ii'lelli't, Illlt "IH <■ '■. <> ri mn; tje.'.;! i ι! \ ' adjacent lighting elements is switched on (quasi-analog Light strip display).

Although there has been a large number of digital display units for some time, there is also a need for analog displays that contain no moving parts. Analog displays are used particularly advantageously wherever tendencies need to be recognized, e.g. during comparison processes. Another area of application is where a rough overview of certain operating states is to be given, e.g. B. for temperature or fill level controls. A particular advantage over numeric displays is that critical points can be marked on the analog scale so that exceeding these points is recognized immediately. The quasi-analogue light strip displays should therefore not compete with the high-resolution digital displays, but merely complement them in a meaningful way. Since the main application is in use as a miniature control instrument, which is used instead of a pointer instrument, there is a requirement for the control circuit to convert an analog input voltage into digital control signals in the simplest possible way so that the connected Leuchlelementc in the form of a more or less long light band.

It is known to meet the requirements in such a way that a chain of comparators is built up with equidista.it increasing voltage thresholds, to which the input voltage is fed as a comparison voltage. Each comparator is assigned a light element (e.g. light bulb, luminescent diode, liquid crystal) in such a way that the order of the light elements corresponds to the order of the compai ators. Integrated circuits that work in this way have already been announced by various companies [1,2,3]. The disadvantage of this method is that a large number of lines and trigger transistors are required. For η Leuchtclcnu lic you need (n + 1) lines and /) control transistors. For this reason, the luminescent strips indicated up to now only have 5 to 12 luminous dots.

The invention is based on the object of creating a control circuit which is analog The input voltage is converted into digital control signals in such a way that with as little technical as possible Effort can control a larger number of lighting elements, the number of control lines should be significantly less than the number of l.lighting elements.

This object is achieved according to the invention in that the light elements of the quasi-analog light strip display in the form of double indexing (i, k) =

(U), (1.2 Ί (2.1), (2.2) (n, m) continuously

are numbered consecutively and the individual elements with their one connection, hereinafter referred to as anode, are assigned to the first code position and with their other connection , hereinafter referred to as cathode, are assigned to the second code position , with anode lines with the same number and cathode lines mn with the same number each connected in parallel * be, and dal! the control of the display takes place according to a time-division multiplex process, in that those I mi htelemen'e are activated jointly on the anode side, the first code number / is the same , with the cathode-side control being carried out in such a way that all IJ elements of the anode-wired activation

th quantity light up whose position number is less than or equal to the number that defines the end of the light strip part to be brightened and is thus assigned to the analog input variable. If the multiplex frequency is chosen to be sufficiently high, the viewer will see a flicker-free display. If η assigns first-digit code numbers to π and m two-part code numbers, you can operate nxm light elements with just n + m control lines. The least amount of lines is required if η = m is selected. In a further embodiment of the invention it is proposed that the first-digit code numbers; be sequentially switched through with a modulo-n counter and connected decoder and determined with the help of a KomparatorkeUe of the type described immediately, ie without prior coding and intermediate storage of the total information, from the first-digit code number and the analog input variable, the combination of the digital cathode control signals will. Only m comparators are required for η χ in elements. In terms of circuitry, the simplest way to realize the cathode control signals directly is to use a digital-to-analog converter and an analog subtracter to subtract the full voltage range of the comparator pins from the input voltage (il) times and feed the rest of the comparator pins.

The advantages achieved by the invention are in particular that one generates the control signals for time-division multiplexing of several parts of a light strip with a simple control circuit directly from the analog signal without prior coding and intermediate storage, which makes it possible to add nx m light elements with n + m control lines operate. In this way you can achieve a much better resolution than before with little circuitry effort.

An embodiment of the invention is shown in the drawing. The figure shows the block diagram of the control circuit for a light strip 7, which consists of 16 elements in the example. The elements are labeled Lu, Li2 ... Lm. Both polarized and non-polarized elements come into consideration as lighting elements. The light bulb symbols used are intended to characterize any lighting element. For a better differentiation, the connections at the top in the picture are referred to as anodes and the bottom connections as cathodes, without loss of generality. The anodes of the elements Ln to Lu are connected to the output line Ai of the decoder 6, the anodes of the elements Ln to L24 to the output line A2, the anodes of the elements L31 to L34 to the output line A3 and the anodes of the elements Ln to L44 to the Output line A ₄ , the cathodes of the elements Lw, L>. \, L31 and Ln are connected to the output line K \ of the comparator 5, the cathodes of the elements L12, L22, Ls2 and Ln to the output line K2, the cathodes of the elements Li 1, L ₂₃ , Ln and Lii with the output line K _s and the cathodes of the elements Lu, L ₇₄ , L ₁₄ and Im with the output line Ka- The control of the Leuchtelc mentes L, k happens / .. B. in the way, that the line Α is connected to the operating voltage by means of a transistor switch built into the decoder 6, while the line Kk is connected to the Moiinniontiüi by means of a transistor switch built into the comparator unit 5.

In order to implement multiplex operation, the output of a clock generator 1 is connected to the input of a modulo-n counter, in this case the modulo-4 counter 2, which works, for example, in Duai code. The outputs of the counter 2 are connected on the one hand to the input of the 1-out-of-n decoder 6. The task of this decoder is to process the dual-coded number ζ at the input so that only line Ai is activated when the count is 00, line A ₂ is activated when the count is OL, line A3 when the count is LO and line A when the count is LL _; . So there is the relationship Z = II.

The output of the counter 2 is now connected, on the other hand, to the input of a digital-to-analog converter 3, which supplies an output voltage (il) L / _re / proportional to ζ and thus to 1-1. With the relatively low number of stages, this digital-to-analog converter can be implemented in a very simple manner. The output voltage (i - \) U _n f of the digital-to-analog converter 3 is supplied with a negative sign to the analog working adder stage 4, at whose second input the input voltage U _c to be converted is given with a positive sign. The output voltage Uk = L / _c .- (i-1) L / _ri - / adder 4 serves as an input voltage of the four-stage in this example KomparatorkeUe 5. The correct operation of the circuit, the illumination that is proportional to the input voltage Uc number of Leuchteiementen of left to right, results when the full voltage range of the comparator pin 5 is chosen equal to U _n - /. In this way, the entire input voltage range U _cm a \ is subdivided into π coarse steps of height Urci with m fine steps of height U _K ilm in each case. In the case chosen here, η = m = 4

IJrci = -. ίΛ - ,,,,, «and the smallest step height -.U _n -r =

The function of the circuit will now be explained for the case that U _c hc '\ 10 / Ib t / _c . ,"." lies.

In the first clock interval let /. = 0. This means that i = 1, and the Leuchielement.e Ln to Lu are activated on the anode side via the line Ai. The voltage is applied to the input of the comparator pin 5

V _K = U, - 0 ■ U _n ., = I, -

10,

16 '""'

This value is greater than U _K i =., U ₁ -max- As a result

all cathode lines K ₁ to K * are activated. However, since only Ai of the anode lines is activated, the first four elements Li 1 to Ln light up.

In the second clock interval ζ = 1. This means that i = 2 and

This value is also larger than U _r ci Therefore turn all Kathodenlcitungen be activated. Since the anodic connection A ₂ is now activated, the elements /.21 to Lm light up.

In the third clock interval is / = 2. This means that ι = 3 and

So Uk lies in the middle of the voltage range

the comparator chain 5. This activates the cathode lines K \ and Kj , while Kz and K ^ remain off. In this clock interval, only the two elements L ₃ 1 and L32 light up.
In the fourth clock interval

This voltage is less than the lowest comparator threshold. This leaves all cathode leads switched off, and no light element lights up in this time interval.

In this way, the first 10 light elements are switched on one after the other, as required Corresponds to the light band function.

It is possible to easily expand the display area by lining up identi make shear circuits with their associated display units by adding the adder 4 mil uses the full voltage range of the converter with the corresponding voltage range for the higher ranges Weight to subtracter.

In some cases it is desirable to adapt the light intensity of the light strip to the surrounding light wedge. For this purpose, the circuit can be modified in such a way that the transistor circuits at the outputs of the comparator chain 5 are replaced by switched constant current sources whose current intensity is controlled with the aid of a light-sensitive element.
Literature:

[1] N.N .: Analog indicator uses ICs and LED's Electronics, 48, No. 3 (1975), p. 8E.

[2] Application note Siemens UAA 180 (1974).

[3] Application Note Texas Instruments SN 16889 P (1975).

1 sheet of drawings

630

Claims (5)

Patent claims: 1. Control circuit for quasi-analog light strip displays, characterized in that the light elements in the form of a double indexing (i, k) = (1,1), (1/2), .., (2,1). (2,2), .. " (ajn) are consecutively numbered and the individual elements are assigned with their anode-side connection to the first code position and with their cathode-side connection to the second code position, with anode lines with the same number and cathode lines with the same number being connected in parallel , and that the control of the display takes place according to a time-division multiplex process, in that those light elements are activated one after the other on the anode side, whose first code number / is the same, while at the same time the cathode-side control takes place in such a way that all elements of the anode-side activated set light up whose position number is less or less is equal to the number that defines the end of the light strip part to be brightened and is thus assigned to the analog input variable. 2. Control circuit according to claim 1, characterized in that the first digit code numbers / sequentially switched through with a modulo-n counter and connected 1-out-of-n decoder and that with the help of a comparator chain with equidistantly increasing threshold values the combination of the first digit code number / and the analog input variable digital cathode control signals is determined. 3. Control circuit according to claim 1 and 2, characterized in that the direct determination The cathode control signals are done by using a digital-to-analog converter and an analog addict stage from the input voltage (/ '- l) times the full voltage range subtracts the comparator chain and supplies the remainder to the comparator chain. 4. Control circuit according to claim I, characterized in that the Multipkxfrcqucnz so high it is chosen that for the viewer a color free Image is created. 5. Ansteuerschahung according to claim 1, 2 and i, characterized in that the analog: adding stage mn is used for this, from the input voltage 1 to / times the full range of the Subtract converter / ι to get a Bcp; iehscrwciteriing by the factor (. '·') - 1) thereby /: u enable f / · t 1) identical luminous band displays including Λ ι! control circuit strung together were en. (] '\ nsteiierscli: i ^! ' men: -
, iussei ι dui i-liiil iing 'i.ich Aiispnicl "1. thereby the light intensity of the l.cuchtele ung i \ vv \ Inifeldhclligkeil is adapted to the ίnisscii.