GB2029073A

GB2029073A - Electronic organs

Info

Publication number: GB2029073A
Application number: GB7841863A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1978-08-23
Filing date: 1978-10-25
Publication date: 1980-03-12
Also published as: IT7950072A0; IT1120528B; DE2934182A1

Abstract

An electronic organ has a keyboard including a printed circuit 12 having a plurality of conducting areas 14 and a strip 20 of conducting rubber foam, or silicon powder with rubber or silver powder with epoxy resin, or copper foil or tin foil above the conducting areas and spaced from them by a spacer 16. The conducting rubber foam, or silicon powder with rubber or silver powder with epoxy resin, or copper foil or tin foil is attached to a strip 22 of nylon or polyester cloth or any similar material or high quality paper to which pressure may be applied to cause the foil to contact a predetermined conducting area 14, and thus to present a predetermined electrical resistance to the oscillatory circuit of the organ which produces a preselected musical note. <IMAGE>

Description

SPECIFICATION Electronic organs The invention relates to electronic organs, in particular those of the type known as miniature electronic organs and is particularly concerned with the keyboard of such organs.

For reasons of both financial economy and limited space it is desirable for a miniature electronic organ to have a keyboard that is not of the type usually incorporated in full size electronic organs in which there are provided a number of keys each of which is independently movable to produce a predetermined musical note. One solution to the problem has been to provide the keyboard in the form of a number of exposed conducting areas each of which is associated with a respective electrical resistance forming part of a resistive network connected to an oscillatory circuit, the circuit being completed by contacting a desired conducting area with a stylus attached to a trailing electrical lead.Such a construction has the disadvantage that if it is required to sequentially produce two notes whose conducting areas are some distance apart, there will inevitably be a time interval between the two notes, and different fingers cannot be used to play different notes.

According to the present invention an electronic organ has a keyboard, an oscillatory circuit and a plurality of electrical resistors which may be connected in selected combinations to the oscillatory circuit to produce predetermined musical notes, the keyboard including a base supporting a plurality of fixed contacts and a flexible conductor situated above the said conducting areas and normaliy spaced therefrom by spacing means and secured to the underside of a strip of flexible material, the keyboard being so constructed and arranged that application of pressure to the upper surface of the flexible material causes the flexible conductor to move into contact with a selected fixed contact and thus to present a predetermined electrical resistance to the oscillatory circuit.

In one form of the invention each of the fixed contacts is of one polarity and is associated with a respective second fixed contact of the other polarity, the flexible conductor being arranged to selectively bridge each pair of associated fixed contacts.

In a further form of the invention each of the fixed contacts is of one polarity and the flexible conductor is connected so as to be of the other polarity and arranged to selectively contact each of the said fixed contacts.

Further features and details of the invention will be apparent from the following description of certain specific embodiments given by way of example only with reference to the accompanying drawings in which: Figure 1 is a diagrammatic partial sectional elevation of the keyboard of a miniature electronic organ in accordance with the invention; Figure 2 is a diagrammatic plan view of the layout of the conducting areas of the keyboard shown in Fig. 1; Figure 3 is a block diagram of the electronic circuit of the organ; Figure 4 is a diagram of the resistive network associated with the keyboard for producing different musical notes.

Figure 5 is a view similar to that of Fig. 1 of a modified construction of the keyboard; and Figure 6 is a plan view of an alternative arrangement of the conducting areas of the keyboard.

The organ comprises a casing having a keyboard, the casing accommodating the electronic circuit shown in Fig. 4 including a loudspeaker 10, the resistive network shown in Fig. 3, and means for supplying power to the electronic circuit, which may be either a battery, or a transformer and a rectifier for mains operation.

As seen in Fig. 1, the keyboard comprises a circuit board 1 2 carrying a number of fixed contacts constituted by separated printed conducting areas 14 arranged in a line and associated in pairs as will be explained in more detail below. As best seen in Fig. 2 the line of conducting areas 14 is covered by an elongate strip of flexible insulating material 1 6 in which a plurality of rectangular holes 1 8 are formed to expose adjacent edges of each pair of conducting areas 1 4. Situated above the insulating material is a thin flexible strip of conducting material 20 (not shown in Fig. 2 for the sake of clarity) which in this case comprises copper foil, which is secured, for instance by adhesive, to a strip of nylon cloth 22.The upper surface of the nylon cloth is smooth and continuous and forms the keyboard surface.

When pressure is applied to the keyboard over a hole 1 8 for instance at the point indicated by an arrow in Fig. 1, the copper foil is pushed down into the hole 1 8 in the insulating material 1 6 and bridges the two contacts or conducting areas 1 4 whose edges are exposed by the hole.

As shown diagrammatically in Fig. 3, one of each pair of conducting areas 1 4 is connected to a common line 24, which in this case is at earth potential, whilst the other of each pair is connected to a respective junction between two variable resistances 26, the variable resistances being all connected together in a resistive network or ladder shown in Fig.

3. The resistive network has terminals X and Y connected to the electronic circuit shown in Fig. 4 whose output frequency varies in dependence on, inter alia, the value of Rx, which is the instantaneous value of the resistance presented by the entire resistive network shown in Fig. 3.

In this specific example each of the variable resistances 26 is of 100 Kilohms, and by varying these and variable resistances in the electronic circuit it can be arranged that when any given pair of conducting areas 14 is bridged the resistance Rx between the points X and Y is such that the output of the electronic circuit delivered to the loudspeaker 10 is a predetermined musical note.

The circuit shown in Fig. 4 comprises two 1 2' both 555 integrated circuits 1C, and 1C connected as free-running multivibrators. In operation, each of these integrated circuits depends on the charging and discharging of a capacitor C1 or C5 connected to pins 2 and 6 of the circuit. The capacitor charges from the positive supply rail through resistors R3 and R4 (in the case of 1C2, for example), until its voltage is equal to that on pin 5 of the integrated circuit. Pin 7 of the integrated circuit is then connected by the integrated circuit to ground, so that the capacitor discharges again through the resistor R4. When the voltage on the capacitor falls to half the voltage on the pin 5, the pin 7 is once again allowed to float, so that the capacitor recharges.Thus, it will be seen that the frequency of oscillation is determined by the resistor and capacitor values, and by the voltage on the pin 5. In the case of 1C2, the voltage on pin 5 is determined internally by the integrated circuit as two-thirds of the supply voltage, since the only external connection to this pin is a stabilising capacitor C4.

However, in the case of 1 cm, the voltage on the pin 5 is modulated by the output of the integrated circuit 102, which is a square wave; to achieve this modulation, an adjustable resistor R2 leads from the output pin (pin 3) of 102 to pin 5 of 1C,. A stabilising capacitor C2 is also connected to pin 5 of 1C,.

Thus in operation, the output of the integrated 1C, is a square wave, at a frequency which is varied around a mean frequency determined by the timing components C" R, and R,. The frequency at which the variation occurs is determined by the timing components C,, R3 and R4. The output is taken from pin 3 of 1C,, and is connected to a loudspeaker 10 through a large value capacitor C.

As mentioned above, the keyboard, which is constituted by the upper surface of the nylon cloth 22, is smooth and continuous, and also bears markings to indicate the note that will be produced when the pair of conducting areas beneath that marking are bridged by the copper foil 20. Although it is of course necessary that the nylon cloth and copper foil move in order to bridge a pair of conducting areas, such movement is equal only to the thickness of the insulating strip 14 which is made as thin as it possible whilst ensuring that accidental bridging of the conducting areas is not possible.

Fig. 5 shows an alternative construction of keyboard in which the conducting areas 1 4 are also arranged in line of the circuit board 1 2. In this case however each conducting area is associated with a junction between two variable resistances 26 in the resistive network and the strip of copper foil 20 is itself connected to earth. Thus when pressure is applied to the keyboard, for instance at the point indicated by an arrow, the copper foil 20 will contact the conducting area 1 4 beneath the point of contact and a circuit will be completed with the result that Rx will assume a predetermined value and the organ will produce a predetermined musical note.

It will be appreciated that the conducting areas may be of a variety of different shapes and may be arranged in a number of different configurations. Fig. 6 shows one such modified arrangement in which the conducting areas are associated in pairs, one conducting area 14 of each pair being generally F shaped and connected to the junction between two resistances of the resistive ladder whilst the other conducting area has two arms parallel to those of the F connected to a common line at earth potential. Overlying the conducting areas is an insulating strip 1 6 in which are formed a plurality of holes 1 8. The advantage of such a layout is that the area of the keyboard which can be pressed to obtain a particular note is somewhat greater whilst the "dead" area between notes is somewhat smaller.

In a further modification which is not illustrated the conducting areas or associated pairs of conducting areas are arranged in two parallel rows having a respective copper foil above it. This permits the surface of the keyboard to be marked black and white in the manner of a conventional keyboard.

In a preferred construction the circuit board is a printed circuit board on which the conducting areas are printed. The function of the insulating strip 1 6 may be fulfilled by a number of separate insulators but is preferably of sheet plastics material. The conductive sheet 20 may be of conducting rubber foam or any material with adequate conductivity and flexibility. As an alternative to nylon cloth, the surface of the keyboard may be of high quality paper, or any appropriate material having the necessary flexibility.

Claims

1. An electronic organ having a keyboard, an oscillatory circuit and a plurality of electrical resistors which may be connected in selected combinations to the oscillatory circuit to produce predetermined musical notes, the keyboard including a base supporting a plurality of fixed contacts and a flexible conductor situated above the said fixed contacts and normally spaced therefrom by spacing means and secured to the underside of a strip of flexible material, the keyboard being so constructed and arranged that application of pressure to the upper surface of the flexible material causes the flexible conductor to move into contact with a selected fixed contact and thus to present a predetermined electrical resistance to the oscillator circuit.

2. An organ as claimed in Claim 1 in which the said fixed contacts are arranged in two substantially parallel lines and the keyboard includes two flexible conductors, one associated with each line of fixed contacts, connected to a common strip of flexible material.

3. An organ claimed in Claim 1 or Claim 2 in which each of the said fixed contacts is of one polarity and is associated with a respective second fixed contact of the other polarity, the flexible conductor being arranged to selectively bridge each pair of associated fixed contacts.

4. An organ as claimed in Claim 3 in which each fixed contact of each pair has two or more arms substantially parallel to, and intercalated with those of the other fixed contact of the pair.

5. An organ as claimed in Claim 1 or Claim 2 in which each of the said fixed contacts is of one polarity and the flexible conductor is connected so as to be of the other polarity and arranged to selectively contact each of the said fixed contacts.

6. An organ as claimed in any one of the preceding Claims in which the fixed contacts are formed as printed conducting areas on a printed circuit board.

7. An organ as claimed in any one of the preceding Claims in which the spacing means comprises a sheet of insulating plastics material having holes formed in it to expose at least part of each fixed contact.

8. An organ as claimed in any one of the preceding Claims in which the flexible conductor is conducting rubber foam or silicon powder with rubber or silver powder with epoxy resin, or copper foil or tin foil.

9. An organ as claimed in any one of the preceding Claims in which the sheet of flexible material is formed of nylon cloth, or polyester cloth or high quality paper.

10. An organ as claimed in any one of the preceding Claims in which the said electrical resistors are adjustable.

11. An electronic organic substantially as herein described with reference to Figs. 1 and 2, or Fig. 5 or Fig. 6.