METHOD FOR SETTING A TIMER CIRCUIT AND DEVICE IN SUCH A TIMER CIRCUIT

Abstract: The invention relates to a method and a device for setting a timer circuit, especially in a fuse (lb), there being used a setting unit (la) for the trans­ fer of setting signal to the timer circuit which is housed in the fuse (lb). For the purpose of simpli­ fying the communication between the fuse (lb) and the fuse setting unit (la), both as regards to avoi­ ding previous calibration of the time reference of the system, and as regards a reduction of the elec­ tro-mechanical contact connection between the fuse (lb) and the setting unit (la) to a mimimum, it has according to the invention been suggested that there are provided setting signals such that the time to which the timer circuit is to be set, is transfer­ red from the setting unit (la) to the fuse (lb) by pulse width modulaton of the power supply voltage. The setting signal can then be transferred via only two contacts (Kl, K2) on the surface of the fuse. The modulation can be to the fact of increasing the power supply voltage from a certain first value (V+) to a higher value (V++) and back to the first value (V+).

Description: BACKGROUND OF THE INVENTION FIELD OF THE ART The present invention relates to a method for setting a timer circuit, especially in a fuse, there being used a setting unit for transferring the setting signal to the timer circuit. The invention also relates to a device in such a timer circuit. PRIOR ART STATEMENT Usually, the communication between the setting unit and the timer circuit in a fuse will be implemented by means of electro-mechanical contact connections on the outer surface of the fuse. However, in connection with such galvanic con­ nections the possibility for contact problems will be pre­ sent and increase with the number of contact points. It is therefore desired to reduce the number of contact connecti­ ons to a minimum. Conventional electronic digital timer circuits or stop watches in a fuse are based on the principle that the timer circuit is set by means of a number of time related pulses which correspond to the set time (frequency setting) of the timer circuit. In order to achieve a sufficient accuracy the time references in the setting unit and the fuse must be synchronized, a fact which involves that one of the two units must be calibrated in relation to the other. This seems to be an unnecessary procedure, and it also complica­ tes the communication between the programming unit in the timer circuit and the setting unit. SUMMARY OF THE INVENTION The object of the present invention is to provide a timer circuit for a fuse, in which the connection between the fuse and the setting unit is substantially simplified in relation to previous structures. Further, the invention has for an object to provide a timer circuit in which the set­ ting thereof can take place without previous calibration of the time reference of the system, i.e. independent of the clock oscillator which is included in the timer circuit. The object of the present invention is achieved in a method of the type stated in the preamble, by which there are pro­ vided setting signals in the form of modulated power supply voltage. By such a technique the setting signals are transferred to the fuse from the setting unit via two contacts on the sur­ face of the fuse. One of the contacts can then transfer electric power to the fuse, the power supply voltage at the same time having sup­ er-imposed thereonto the data corresponding to the setting value which is to be given to the timer circuit. As a set­ ting signal or data signal there can for example be used a power supply voltage which exceeds a certain reference vol­ tage. Simultaneously with the modulation of the power supply vol­ tage there takes place a corresponding current modulation of the current consumption of the fuse, and this current modulation or variation in the current consumption will be detected by the setting unit as control signals. The other contact on the surface of the fuse connects the return conductor to a reference, for example metal, and with this two-contact solution it is possible to simulta­ neously transfer data signals both ways. Calibration of the time reference in the system is avoided since the time to which it is desired to set the timer cir­ cuit, is transferred as a pulse which is pulse width modu­ lated (period setting), the length of this pulse exactly corresponding to the set time devided by a known factor. As long as there is present a setting signal, which corre­ sponds to the above mentioned pulse, a clock oscillator provided in the fuse will provide pulses which are counted by a counter and stored in a memory, the duration of the setting signal corresponding to a predetermined time set­ ting devided by a known factor. An unknown number of inter­ nal clock pulses will thus be counted by the counter as long as the programming pulse remains. If the fuse resides in a launched projectile the counter will start its down counting immediately after launching. The internal clock frequency will then be devided by the known factor, such that the timer circuit now will obtain a running time cor­ responding to the correct time. This involves that the clock oscillator being used in the timer circuit, only needs to have a good short time stability, whereas long time stablility and variations from fuse to fuse can vary within wide limits. Appropriately, the oscillator frequency can be stipulated on the basis of a predetermined resolution in the timer circuit and a division factor given by the setting unit. A device in a timer circuit of the above type will comprise features which are more closely defined in the appended claims. BRIEF DESCRIPTION OF THE DRAWING The invention will now be further described, reference being had to the drawing which illustrates an embodiment of a timer circuit according to the invention. Figure l is a block diagram of an embodiment of a timer circuit according to the present invention. Figure 2 illustrates the signal course at various positions in the block diagram of Figure l, in which hatched areas show the control signal which current modulates the power supply voltage. DESCRIPTION OF PREFERRED EMBODIMENT Firstly, the course of events in the setting phase or the programming phase will be discussed. In Figure l there is illustrated a setting unit la and a unit comprising a timer circuit, for example a fuse which is here illustrated by the dashed line lb. The setting unit la is connected to the fuse lb via the contacts Kl and K2, and after contact as been achieved between the setting unit la and the fuse lb, the setting or the programming of a timer circuit in the fuse lb can commence. In Figure 2 there are illustrated various signal courses, and the line designated Kl for the upper signal course of Figure 2 represents the signal communication between the setting unit la and the fuse lb. This communication signal can appropriately be a modulated power supply voltage, a voltage being applied after having obtained contact between the setting unit la and the fuse lb, such that the fuse lb is supplied with a voltage V+ via the contact Kl in rela­ tion to the contact K2. The modulation of the supplied voltage V+ can be an increase of the voltage from V+ to a higher voltage V++, and back to V+. In other words there can as data signals be used a power supply voltage excee­ ding a certain reference voltage according to a given pat­ tern. The timer circuit which is housed by the fuse lb, comprises a detector 4 which detects whether a switched on setting unit la is connected to the fuse lb for supplying electric power to the fuse. The detector 4 can for example be con­ structed as a current detector detecting current above a certain value. To the detector 4 there is connected a regulator 5 which regulates the supply voltage to the fuse, the internal non-­ regulated supply voltage being supplied via the contact 3 through a diode l4 and to the regulator 5. During the pro­ gramming phase the internal voltage source will not be ac­ tive, and there will then be no current from the contact 3. The diode l4 serves to prevent unnecessary current consump­ tion from the setting unit la. The output from the regulat­ or 5 will during normal operating conditions via the con­ tact K6, supply all the electronic circuits which are con­ nected to the time setting circuit in the fuse lb. In the fuse lb there is also included a feedback circuit 8 which via its terminal K9 will reset the electronic circuitry each time the regualtor 5 is switched on. When the fuse lb is supplied with voltage from the setting unit la, the detector 4 will, via a buffer ll, set the con­ trol logic l5 to a programming mode. At the same time a current switch 7 will be enabled to function when a signal from a pulse comparator l0 which is connected to the one input contact Kl, and/or the control logic l5, is sent out to said current switch 7. When the supply voltage is switced on, an oscillator l2 will start oscillating. The oscillator l2 is appropriately a free running oscillator having a good short time stabili­ ty. The output from the oscillator l2 is connected to a divider unit l6 and a frequency selector l7. The oscillator frequency is determined on the basis of a desired resoluti­ on in the timer circuit and the dividing factor in the setting unit. A suitable resolution can for example be 0.l second, and the dividing factor l000 times, a fact which involves that the oscillator must operate with a frequency of minimum l0 kHz. Because the control logic l5 is set to programming mode, the frequency selector l7, upon signal from the control logic l5, will be set to select an input signal direct from the oscillator l2. When the timer circuit depicted in Figure l is reset, it is made ready for setting of the time in question. The setting of the fuse, i.e. the timer circuit in the fuse, is in the disclosed proposal for solution implemented with two pulses A and B, as this appears from the signal diagram at the top of Figure 2. Pulse A gives information about programmed time, the length of pulse A corresponding to the accurately set time divided with a known factor. If this factor is made equal to l000, and if it is desired to set the timer circuit to l00 seconds, the pulse A will have a duration of l00 milliseconds. Pulse B is a write pulse, which entails that the set information is stored in a memory. When the pulses A and B, respectively, are supplied to the fuse, they will be detected by the pulse comparator l0. A signal Sl3 from the pulse comparator l0 will then close the current switch 7 as long as the pulses remain. The additio­ nal current consumption which is caused by the current switch 7 at the output from the detector 4, will be regis­ tered by the setting unit la, and in this manner one will quickly get a response to whether larger parts of the elec­ tronic circuitry in the fuse operate satisfactorily. During this first part of this programming phase the con­ trol logic l5 will be controlled by the signal Sl3 as a pace setter. The control logic l5 enables a gate l8 to be opened for clock pulses from the frequency selector l7 to a counter l9 as long as the pulse A exists. After the termi­ nation of pulse A, what has been stored in the counter l9 will be an unknown number of clock pulses which are propor­ tional to the duaration of the set time in the fuse setting unit la. The pulse B enables the control logic l5 to send a write pulse to the memory 20, and the contents of the counter l9 will then be stored in for example non-volatile transistor cells in the memory 20. After the reading into the memory 20, the first part of the programming phase is terminated, and one will thereafter pass on to a checking phase. The control logic l5 will then be controlled by an internal pace maker which is tapped by the divider unit l6. The control logic l5 will then run through an inherent routine, the starting thereof being transferring the contents of the memory 20 to the counter l9. The counter l9 then starts its down counting, and the frequency selector l7 selects an input signal direct from the oscillator l2. The control logic opens the gate l8 to allow the counter l9 to start its down counting, there being provided a pulse C on the signal line Sl3. Pulse C will the have a duration corresponding to the time it takes to count down the counter l9 to zero. Pulse C on the signal line Sl3 will effect the current switch 7 to close as long as pulse C exists. Pulse C will be detected by the setting unit la and will compare the length of pulse A with pulse C. If the oscillator l2 has had a constant frequency throughout the complete programming phase, pulse C will have the same duration as pulse A, a fact which is checked by the setting unit la. The control logic l5 and the counter l9 are both connected to an output buffer 2l, and the control logic l5 will cater for no activity of the output buffer 2l during the program­ ming phase. After comparison and control of the pulses A and C, the programming phase is completed, and the set­ ting unit la will switch off the power supply to the fuse lb, whereafter the setting unit is removed from the fuse. If the above mentioned timer circuit resides in a projecti­ le, the trajectory thereof will commence at the moment of discharge, the internal supply voltage being supplied via the contact 3. The regulator 5 will then supply the elec­ tronic circuitry with electric power via the output K6, whereas the resetting circuit 8 will reset the electronic circuitry, and the oscillator l2 will start oscillating. The detector 4 will now register that no fuse setting unit is connected to the fuse and will set the control logic l5 to trajectory mode via the buffer ll. The control logic l5 adjusts the frequency selector l7 to select clock pulses from the divider unit l6. This involves that the pulse length which the data in the memory 20 represent, now will be multiplied by the same factor which was used in the fuse setting unit during the programming of the timer circuit. If the oscillator frequency from the oscillator l2 is the same as during the programming phase, the running time of the timer circuit will correspond to the time being set on the setting unit. The control logic l5 will immediately after the resetting of the electronic circuitry run through an inherent routine, it now being controlled by the same internal pace maker as during the checking part of the pro­ gramming phase. What will happen now, is that the contents of the memory 20 in first instance will be transferred to the counter l9 which has been set to down counting, where­ after the gate l8 will open and the counter l9 commence to count down. The output buffer 2l will now be enabled to re­ ceive signal from the counter l9. When the timer circuit has run out in that the counter l9 has counted down to zero, it will output a signal to the output buffer 2l. The output 22 will now be activated and the trajectory phase terminated. It is to be understood that the above described embodiment only illustrates an arbitrary proposal for solution, only one counter and one memory being used therein. However, it is of course possible to include a further memory and/or counter for achieving av greater flexibility and security. The counters and/or memories can either be programmed si­ multaneously with pulse A and pulse B, or they can be pro­ grammed in series by means of a new pulse from the setting unit, this new pulse appearing between pulse A and B and giving information to the counter and/or memory number 2. It can often be desired to have a fixed time which has to run out before the output buffer 2l is activated. If this is implemented as a hardware programmed counter, it will constitute a fair contribution to the safety if the memory 20 with non-volatile transistor cells should possibly fail. The accuracy of such a counter will, however, be dependent on the long time stability of the oscillator l2. It is also possible to set the timer circuit to various modes. This can be done in that the setting unit supplies to the fuse a new pulse after pulse A. The control logic l5 will compare the length of this pulse with the pulse dura­ tion of the internal time reference in the fuse by tapping a signal from the down counter l6 at an appropriate locati­ on. The result can be stored in separate l-bits non-volati­ le transistor cells when the write pulse B is supplied. By an appropriate design of the control logic l5 it is pos­ sible to read all the programmed times and modes of the setting of the fuse during the checking part of the pro­ gramming phase. It is also possible to read the programmed times and modes without a previous setting of the fuse. It is to be understood that the principle of setting the timer circuit by means of pulse width modulation (period setting) also can be used where the setting signal is transferred by means of electro magnetism, radio waves or light. Combinations of variations in solution can render a very versatile timer circuit. The timer circuit can operate alone or in a timer fuse or be combined with proximity and impact functions.

Claims: 1. Method for setting a timer circuit, especially in a fuse, there being used a setting unit for transfer of set­ ting signals to the timer circuit, and being provided set­ ting signals in the form of modulated power supply voltage, characterized in that as setting sig­ nal there is used a power supply voltage (V++) exceeding a certain reference voltage (V+). 2. Method as claimed in claim l, characteri­ zed in that as long as a setting signal is pre­ sent, a clock oscillator in the fuse will be running, the pulses of the oscillator being counted by a counter and stored in a memory, the duration of the setting signal cor­ responding to a predetermined time setting divided by a known factor. 3. Method as claimed in claim 2, characteri­ zed in that the oscillator frequency is estab­ lished on the basis of a predetermined resolution in the timer circuit and a division factor given by the setting unit. 4. Method as claimed in any of the preceding claims, characterized in that the time set­ ting(s) and possible modes in which the fuse is to be set, are implemented by pulse width modulation of the modulated power supply voltage signals. 5. Method as claimed in any of the preceding claims, characterized in that by modulation of the power supply voltage there takes place a correspon­ ding current modulation of the current consumption of the fuse, and that this current modulation is detected by the setting unit as control signals. 6. Device in a timer circuit, especially in a fuse, the timer circuit being set by means of a setting unit (la) which is connected to the fuse (lb) for transfer of the setting signals to the timer circuit, the device comprising a modulator for modulating the power supply voltage, characterized in that the modulator modulates the power supply voltage between a reference vol­ tage (V+) and a higher power supply voltage (V++). 7. Device as claimed in claim 6, characteri­ zed in that the device comprises a clock oscil­ lator (l2) which via a frequency selector (l7) is connected to a counter (l9) which during the presence of the setting signal (A) counts an unknown number of clock pulses con­ trolled by the time reference of the fuse for storing the pulses in a memory (20), the duration of the setting signal corresponding to a predetermined time setting divided by a known factor. 8. Device as claimed in claims 6 or 7, characte­ rized in that the memory (20) is connected to a control logic (l5) which is connected to a frequency se­ lector (l7) which in response to a signal from the control logic (l5) during the trajectory phase selects clock pulses from a divider unit (l6) connected to the oscillator (l2), the down counting of the contents of the memory (20) being executed by a counter (l9) which is controlled by clock pulses being divided down by the same factor as used in the setting unit (la), and thereby giving the timer circuit (lb) a running time equal to the time set in the setting unit (la). 9. Device as claimed in any of the preceding claims, characterized in that it comprises a current detector (4) which detects the modulation of the power supply voltage, the current modulation being detected by the setting unit (la) as control signals.

Inventors: KJERSEM, ARVID
Applicants: NORSK FORSVARSTEKNOLOGI A/S
Application year: 1986
Main classification: F42C11
IPC codes: F42C17