AU674216B2

AU674216B2 - Coin validation process

Info

Publication number: AU674216B2
Application number: AU63151/94A
Authority: AU
Inventors: Nicholas Jamons
Original assignee: Alcatel Australia Ltd
Current assignee: Nokia Services Ltd
Priority date: 1993-05-31
Filing date: 1994-05-13
Publication date: 1996-12-12
Anticipated expiration: 2014-05-13
Also published as: AU6315194A

Description

P/100/011 28/5/91 Regulation 3.2

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Invention Title: "COIN VALIDATION PROCESS" The following statement is a full description of this invention, including the best method of performing it known to us:- 0 2 This invention relates to coin validation and in particular to a selfcorrecting coin validation process.

Coin validation dev;ices suffer from the problem that the performance of the components used in the device exhibit long term drift due to ageing of the components, and moreover, to changes to the characteristics of valid coins due to ware after the coins have been in circulation for a long period, and also due to slight changes to the coins when the Mint subsequently produces additional coins to replace those lost or damaged during circulation.

Many coin validation devices identify coins by the change in signal as the coin passes between a coil driven at a known frequency and a detector coil.

The drift problem has been addressed in Australian patent No. 584330, which discloses a method of continuously recalculating an acceptance template from the values of accepted coins. Thus the acceptance template is moved as the component drift takes effect.

15 This specification discloses a technique for correcting the drift without the need to continuously reposition the acceptance template.

A method of adjusting the operation of a coin validator of a coin detector S.il: to compensate for changes in characteristics of a valid coin and/or components of said coin detector, said method including the steps of: p measuring the output from the coin detector when no coin is present to produce an initial datum value; storing ihe initial datum value; storing an acceptance template defining the upper and lower values of 25 acceptable coins at the time the initial datum value was derived; subsequently measuring the output of the coin detector when no coin is present to produce a current datum value; calculating an adjustment factor from the initial datum value and the current datum value; adjusting the output of the detector when a coin is present by the adjustment factor to produce an adjusted value; measuring the adjusted value against the ac eptance template to determine if the coin is acceptable, storing a plurality of readings of each type of coin and repositioning the acceptance template for each coin type in accordance with the distribution of the readings of the respective coins, each acceptance template being centred on the mean of the readings for the respective coin types.

The adjustment factor may be calculated by the use of .n algorithm. In its simplest form, a linear rela ,onship may be assumed, in which case the adjustment factor is the initial datum value, Di, divided by the current datum value, Dc, and the adjusted value, VA, is determined by multiplying the coin present value, by the adjustment factor.

D.

Thus, VA= V. 0

D

C

More complex algorithms may be used if this is required due to non-linear effects or various coin sizes and materials.

The invention will be described with reference to the accompanying 15 drawings in which: Figure 1 is a schematic diagram of a circuit embodying the inventior; Figure 2 shows the acceptance template of a coin type and initial and current datum values.

With reference to Figure 1 the coin validator consists of a driven coil 1 20 and a detector coil 2. The driven coil is driven by an alternating signal source 3. The space between coils 1 and 2 provides a passageway for coins being tested 4 The output of the detector coil is measured by being cor ,erted to a digital signal in A/D converter 4 and applied to processor 6. The signal applied to driven coil 1 is also measured in processor 6, after conversion in A/D converter 5. Thus the relative value of output signal to input signal can be established by processor 6 by dividing the output of A/D 4 by the output of A/D The initial datum value Di can thus be calculated as the initial ratio of the output of A/D4 with no coin present to the output of A/D5. This is stored in memory associated with processor 6. At the same time an initial acceptance template, being upper and lower acceptance limits, is also stored in memory.

As discussed earlier, the value of the components may drift with time.

4*4*4* An evaluation of this drift is made by periodically measuring the current datum value D. with no coin present. Figure 2 shows the acceptance template defined by an upper limit V, and a lower limit VL. The initial datum value Di and current datum value D. are also shown. The ratio of Di to Dr provides a relative measure 15 of the drift and this is used to adjust the reading when a coin is tested. Thus ,.e the reading when a coin is tested is multiplied by D 1 and then tested against the acceptance template.

In a preferred embodiment the acceptance limits for a particular coin can be determined statistically by measuring a plurality (eg. 2500) of coins on a test coin validator and determining upper and lower limits to achieve, eg. 95% pass of valid coins.

These limits may be programmed into a particular coin validator's memory and adjusted to allow for the specific characteristics of the detector circuit after which the adjusted values. become the acceptance template.

The adjustment for each coin validator is necessary due to variation in the manufacture of the devices, Adjustment may be made by manufacturing a coin gauge being a piece of metal of the same characteristics as the mean value of the test limits. The coin gauge is then fed into each coin validator to centre the limits fu each validator. Alternatively, when the window is first calculated a coin could be dropped into the test validator and its reading relative to the window noted and this coin could then be used to position the test limits in eu--ch validacor.

In a further embodiment in a payphone, readings from each type of coin are stored in the memory and can be read out either by display on the payphone's LCID or be downloaded to a remote management centre or a portable memory device carried by a technician. This information may be used to readjust the position of the acceptance template for each type of coin, eg. by calculating the mean of the coin readings and centering the template on this.

Alternatively, where phones are connected to a payphone management system as described in Australian patent No. 624911, the information on coin readings may be transmitted to the payphone management centre processor and used to calculate the new mean for each phone and this information is then transmitted to the phone to re-align the acceptance template.

The information gathered from the coin readings either by the technician or management system can also be used to modify the acceptance template limits, As an alternative the template may be repositioned using the inverse of the adjusting factor, ie. by multiplying the limits by D 0

/D

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Claims

1. A method of adjusting the operation of a coin validator of a i detector to compensate for changes in characteristics of a valid coin and/ ,omponents of said coin detector, said method including the steps of: measuring the output from the coin detector when no coin is present to produce an initial datum value; storing the initial datum value; storing an acceptance template defining the upper and lower values of acceptable coins at the time the initial datum value was derived; subsequently measuring the output of the coin detector when no coin is present to produce a current datum value; calculating an adjustment factor from the initial datum value and the current datum value; adjusting the output of the detector when a coin is present by the 15 adjustment factor to produce an adjusted value; measuring the adjusted value S* against the acceptance template to determine if the coin is acceptable, storing a plurality of readings of each type of coin and repositioning the acceptance template for each coin type in accordance with the distribution of the readings of the respective coins, each acceptance template being centred on the mean of *20 the readings for the respective coin types.

2. A coin validation device ir-luding a coin detector means, measuring means to measure output signals from said coin detector means when no coin is present to derive an intial datum value, memory means for storing said initial **datum value as well as an acceptance template defining upper and lower values of acceptable coins at ihe time said initial datum value is derived, means to derive a current datum value by measuring with said measuring means output signals of said coin detector means when no coin is present, calculation means for calculating an adjustment factor from said initial datum value and said current datum value, adjustment means for adjusting the output of said coin detector means when a coin is present to produce an adjusted value, and 8 comparison means to compare said adjusted value with said acceptance template to determine if the coin is acceptable, storage means for storing a plurality of readings of each type of coin, means for repositioning the acceptance template for each coin type in accordance with the distribution of the readings of the respective coins, and means for centering each acceptance template on the mean readings for the respective coin types.

3. A method of adjusting a coin validator substantially as herein described with reference to the accompanying drawings.

4. A self-correcting coin validator substantially as herein described with reference to the accompanying drawings. DATED THIS THIRD DAY OF OCTOBER 1996 ALCATEL AUSTRALIA LIMITED S S S S «*SS ee* SO i II-- ABSTRACT A method of compensating for performance drift of components in a coin validation arrangement that includes a coin detector and a stored electronic acceptance template (Vu-VI), without the need to continuously re-position the template. The method comprises measuring the output of the detector when no coin is present to obtain an initial datum value (Di) and storing the value; subsequently measuring the output of the detector when no coin is present to obtain a current datum value and calculate an adjustment factor (Di/Dc) from the datum values. The adjustment factor is used to produce an adjusted 9 output of the detector which is measured against the stored acceptance *o e template to determine coin validity. 99 s 9 9 0