GB2028606A

GB2028606A - Solar power pack for electric fence

Info

Publication number: GB2028606A
Application number: GB7928731A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1978-08-18
Filing date: 1979-08-17
Publication date: 1980-03-05

Abstract

A solar powered power pack (with particular utility in powering an electrical animal fence) includes in a single angularly settable housing (1), solar cells (4), a pulse-generating circuit feeding exposed H.T. output terminals (5, 6), a standby dc accumulator, and a mains charger therefor. The mains charger is fed via a mains input connector (8) and the pack includes a switch (7) to select whether the circuit is or is not connected to the accumulator/charger and whether the mains charger is connected to the accumulator. The selector switch can also be used to set whether the H.T. power output is at either of two possible power output levels. <IMAGE>

Description

SPECIFICATION Improved H. T. solar power pack This invention relates to an improved H. T. solar power pack which has particular, but not exclusive, utility as a power pack for an electrical fence to control the grazing area of quadruped animals.

According to the invention an H. T. solar power pack comprises a housing, a plurality of solar cells in the housing, a dc/ac pulse-generating circuit located within the housing having its input connected to the output of the solar cells and its output connected to a pair of H. T. terminals projecting from the housing, a dc accumulator within the housing electrically connected in parallel with the solar cells to take over energisation of the pulse-generating circuit when the solar cells are giving an output less than that of the accumulator and a mains-powered dc charger within the housing for charging the accumulator, the input of the charger terminating in a connector means mounted in the bottom or a side wall of the housing.

Conveniently the solar cells are mounted together below a transparent sheet forming the top wall of a parallelepipedic housing with the H.T.terminals and plug-in connector means mounted in the bottom or a side wall of the housing. Suitably a manually-operated selector switch is also located on the bottom or a side wall, the switch serving to connect the solar cells/accumulator to the input of the pulsegenerating circuit in one position and to disconnect them in another position when the power pack is not in use. The selector switch in yet another position can also be used to put the charger in circuit with the accumulator without energising the pulse-generating circuit.

Preferably the housing is provided with mounting means which permit it to be adjustably secured to a ground-support member in such wise that the solar cells can be variably set relative to the zenith at the location of the ground-support member.

The pulse-generating circuit conveniently comprises an oscillator tuned to some thousands of Hertz (e.g. a push-pull oscillator) arranged to incrementally charge up a capacitor and an electronic switch means to periodically discharge the capacitor through the primary winding of a step-up transformer, whose secondary winding is connected between the H. T. terminals. An H. T.

output consisting of pulses of electrical energy of a peak voltage of a few KV (e.g. between 2 and 5 KV) occurring every second or every few seconds (e.g. between 1-5 seconds) would be typical. Two capacitors of different capacity can be provided for incremental charging from the oscillator output.

When the power pack is used for an electric fence the smaller capacitor can be employed for "normal" use and the larger when operating in a "conditioning mode" (for conditioning animals fresh to a fenced grazing area to avoid the electrical fence). A selector switch for choosing which of the capacitors is in circuit can conveniently be mounted on the bottom or a side wall of the housing.

The solar cells are preferably connected in series and between three and ten cells each of a maximum rated emf of about half a volt is a convenient arrangement.

One embodiment of H. T. solar power pack in accordance with the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of the housing showing the bank of solar cells, the mounting means and the H. T. terminals, and Figures 2 and 3 are schematic diagrams showing the interconnection of the electrical components within the housing.

Referring to Figure 1, the housing comprises a hollow box 1 (e.g. of metal or glass fibrereinforced polycarbonate resin) closed at its top by a transparent lid 2. Below the lid is a plate 3 mounting six solar cells 4. The side of the box 1 supports a pair of H. T. terminals 5 and 6, a six- way selector switch 7 (see Figure 3) and a power lead connector 8. The lid 2 makes a weather-proof seal with the box 1 and the circuit components shown in Figures 2 and 3 are located within the housing and interconnected in the manner shown.

To use the power pack, it is turnably mounted on the upper ends of a spaced pair of posts 9 projecting vertically from the ground. Angular graduations 10 embossed on the ends of the box 1 permit the plane of the plate 3 to be adjusted relative to the horizontal prior to clamping the post 9 to the box 1, to ensure that the solar energy reaching the plate 3 is optimised for the latitude of use.

The output from the series-connected solar cells in the plate 3 is fed to the input of a pulsegenerating circuit 11 when the switch 7 is in positions B or C (shown in Figure 3) and the output of the circuit 11 is connected to the H. T.

terminals 5-and 6. A sealed 2 volt 30 amp accumulator 12 (shown in Figure 2) is also connected to the input of the circuit 11 when the selector switch 7 is in these positions. When the selector switch 7 is in position D, the accumulator 12 is connected in parallel with a mains charger 1 3 whose input is connected to the connector 8.

When the selector switch is in its positions A or F the circuit 1-1 is unenergised and no connection exists between the charger 13 and the accumulator 12. The circuit 11 comprises a pushpull oscillator 14 feeding a step-up transformer 19. When a voltage of about 2.4 volts is applied across leads 1 8a and 1 bob, the circuit 14 oscillates at a frequency in the range 5 to 30 Kilohertz across the primary winding of the step-up transformer 1 9:The secondary winding of the transformer 1 9 steps up the voltage to around fifty volts and via a rectifier bridge 20 and smoothing capacitor feeds this, via a line 22, to the primary winding of a second step-up transformer 21 and a selected one of two different capacitors 23 and 24.The selected capacitor is incrementally charged up with each cycle of the oscillator 14. A thyristor 25 is in series with the primary winding of the transformer 21 and is fed from a triggering circuit which includes unijunction transistor 26. A supply line 27 for the transistor 26 is maintained at about 18 volts by a Zener diode 28. Every time the thyristor 25 is fired a peak voltage in the range 4 to 6 KV appears across the terminals 5 and 6 (typically every one to four seconds).

A low loss diode 29 prevents the accumulator 12 discharging through the solar cells during overcast or night-time conditions.

Although the power pack described can be used for any application where a high voltage pulsed output is required in an open air location, its primary intended use is for energising an electrical fence for animal control purposes. For this application a wire of the fence would be connected to one of the terminals 5 or 6 and the other terminal earthed. The fence wire would be supported by insulating posts (not shown) around an animal grazing area. During the hours of daylight the circuit 11 would be powered primarily from the output of the bank of solar cells, any surplus power being used to top up the accumulator 12. During the hours of darkness, the powering of the circuit 11 is provided soiely by the accumulator and during overcast daylight periods partly by the solar cells and partly by the accumulator.The plug-in connector 8 affords an easy way of charging the accumulator at the beginning of the grazing season, prior to bringing the power pack oust into the grazing area, the selector-switch 7 being moved to position E for this operation. suitably the capacity of the accumulator 12 shourd be sufficient to ensure that it will, unaided, power the circuit 11 for a period of at least 240 hours. In the exemplified circuit the accumulator has a capacity of at least 25 amp/hours. The accumulator capacity depends upon the location of the unit and the box 1 illustrated is large enough to receive an accumulator of capacity 60 amp/hours.

Although the power pack illustrated shows the box 1 supported from a post 9 at each end (which posts, or one of which posts, may be used to electrically earth the circuit 11), it should be appreciated that the box may be supported in different ways. For example a pair of arcuate rods (shown dotted) can be secured to the bottom wall of the box (one rod at each end with each parallel to the end walls and normal to the bottom wall) and a clamping screw on the post 9 may embrace the appropriate rod to fix the box in the determined inclination to the horizontal. With a short box, a single arcuate rod can be used centrally of the bottom of the box and a singie post 9 can be used to support the box from the ground and optionally to earth the circuit 11.

Figure shows the four wafers which make up the selector switch, the wafers being numbered 1, 2, 3 and 4 and shown in brackets below the sketches of the wafers. Position B in wafer 1, for example is designated B, and the central conductor in each wafer is given the letter 0 (thus 03 is the central conductor in the third wafer and can be seen to be connected to the accumulator 12.

From a consideration of the selector switch in Figure 3 and from the foreyoing description it will be seen that in positions A and F nothing is connected via the switch 7. In position B the capacitor 23 is in circuit, the accumulator output is connected to the input of the circuit 11 and the solar cells are connected to the accumulator 12.

This gives an H. T. output in the "normal" mode. In position C, the capacitor 24 is in circuit, the accumulator output is connected to the input of the circuit 11 and the solar cells are connected to the accumulator 12. This gives an H. T. output in the "conditioning" mode. In position D, the capacitor 24 is in circuit, power is supplied to the charger 1 3 and the output from the charger 1 3 is fed to the input of the circuit 1 This gives an H.T. output in the "conditioning" mode powered from the mains.

In position E, the circuit 11 is not energised and the accumulator is connected to the output of the mains-powered charger 13.

Desirably the selector switch 7 is lockable in a chosen position and can only be moved to a different position by use of a key. This arrangement prevents vandals tampering with the switch.

Claims

1. An H. T. solar power pack comprising a housing, a plurality of solar cells in the housing, a dc/ac pulse-generating circuit located within the housing having its input connected to the output of the solar cells and its output connected to a pair of l-i.T. terminals projecting from the housing, a dc accumulator within the housing electrically connected in parallel with the solar cells to take over energisation of the pulse-generating circuit when the solar cells are giving an output less than that of the accumulator and a mains-powered dc charger within the housing for charging the accumulator, the input of the charger terminating in a connector means mounted in the bottom or a side wall of the housing.

2. A power pack as claimed in claim 1, in which the solar cells are mounted together below a transparent sheet forming the top wall of a parallelepipedic housing with the H. T. terminals and plug-in connector means mounted in the bottom our a side wall of the housing.

3. A power pack as claimed in claim 2, in which the manually-operated selector switch is also located on the bottom or a side wall, the switch serving to connect the solar cells/accumulator to the input of the pulse-generating circuit in one position and to disconnect them in another position when the power pack is not in use.

4. A power pack as claimed in claim 3; in which the selector switch in yet another position will put the charger in circuit with the accumulator without energising the pulse-generating circuit.

5. A power pack as claimed in claim 3 or claim 4, in which two positions of the selector switch connect the input of the pulse-generating circuit to the solar cells/accumulator but with a different component in the said circuit in one of those two positions relative to the other, so that the power of the H. T. output from the said circuit is higher in one position than in the other.

6. A power pack as claimed in any preceding claim, in which the housing is provided with mounting means which permit it to be adjustably secured to a ground-support member in such wise that the solar cells can be variably set relative to the zenith at the location of the ground-support member.

7. A power pack as claimed in claim 6 in which the mounting means is electrically conducting.

8. A power pack as claimed in any preceding claim in which the pulse-generating circuit includes an oscillator which is arranged to incrementaily charge up a capacitor and an electronic switch means is used to periodically discharge the capacitor through the primary winding of a step-up transformer, whose secondary winding is connected between the H. T.

terminals.

9. A power pack as claimed in claim 8, in which the H. T. output consists of pulses of electrical energy of a peak voltage of between 2 and 5 KV occuring every 1 to 5 seconds.

10. A power pack as claimed in claim 8 or claim 9, in which two capacitors are provided of different capacity either of which can be switched into the pulse-generating circuit to provide, respectively, a normal mode of operation and a conditioning mode of operation depending on which capacitor is in circuit.

11. A power pack substantially as hereinbefore described with reference to, and as illustrated in the accompanying drawings.

12. An electric fence to control the grazing area of quadruped animals incorporating a power pack as claimed in any prece.ding claim.