Voltage protection circuit for multi-drop bus of an automated coin vending machine

A voltage protective circuit for a component connected as a load to a multi-drop bus in a vending machine comprising:

• a pair of input terminals coupled to said multi-drop bus;
• a pair of output terminals coupled to said component;
• a line connecting one of said input terminals to one of said output terminals;
• first spike prevention means coupled between the pair of input terminals for preventing current spikes above a first predetermined voltage from flowing along said line to said component;
• second spike prevention means connected in series with said line and after said first spike prevention means for preventing current spikes above a second predetermined voltage from flowing along said line to said component, and
• wherein said second spike prevention means comprises a series regulator circuit.

A voltage protective circuit for a coin changer/validator connected as a load to a multi-drop bus in a vending machine comprising:

• a pair of input terminals coupled to said multi-drop bus;
• a pair of output terminals coupled to said coin changer/validator;
• a line connecting one of said input terminals to one of said output terminals;
• first spike prevention means coupled between the pair of input terminals for preventing current spikes above a first predetermined voltage from flowing along said line to said coin changer/validator;
• second spike prevention means connected in series with said line and after said first spike prevention means for preventing current spikes above a second predetermined voltage from flowing along said line to said coin changer/validator;
• and wherein said first spike prevention means comprises a shunt suppressor circuit.

A voltage protective circuit for a coin changer/validator connected as a load to a multi-drop bus in a vending machine comprising:

• a pair of input terminals coupled to said multi-drop bus;
• a pair of output terminals coupled to said coin changer/validator;
• a line connecting one of said input terminals to one of said output terminals;
• first spike prevention means coupled between the pair of input terminals for preventing current spikes above a first predetermined voltage from flowing along said line to said coin changer/validator;
• second spike prevention means connected in series with said line and after said first spike prevention means for preventing current spikes above a second predetermined voltage from flowing along said line to said coin changer/validator;
• and
• wherein said second spike prevention means comprises a series regulator circuit.

A vending machine comprising:

• a DC power supply;
• a machine controller coupled to the power supply;
• a coin changer;
• a multi-drop bus coupling the coin changer to the machine controller, said bus supplying DC electrical power over first and second conductors and supplying communications data over a third conductor;
• and
• a spike prevention circuit interposed along the multi-drop bus between the coin changer and the machine controller,
• said spike prevention circuit comprising:
• a pair of input terminals and a pair of output terminals coupled to the first and second conductors of the multi-drop bus,
• a shunt suppressor coupled across the input terminals so as to be coupled between the first and second conductors of the multi-drop bus, and
• a series regulator coupled in series between respective input and output terminals so as to be coupled in series with one of the first and second conductors of the multi-drop bus.

A vending machine comprising:

• a DC power supply;
• a machine controller coupled to the power supply;
• a coin changer;
• a multi-drop bus coupling the coin changer to the machine controller, said bus supplying DC electrical power over first and second conductors and supplying communications data over a third conductor;
• and
• a spike prevention circuit interposed along the multi-drop bus between the coin changer and the machine controller,
• said spike prevention comprising:
• a pair of input terminals and a pair of output terminals coupled to respective segments of the first and second conductors of the multi-drop bus,
• a shunt suppressor coupled across the input terminals so as to be coupled between the first and second conductors of the multi-drop bus, said shunt compressor becoming conductive in response to appearance across the input terminals of the first and second conductors of the multi-drop bus of a voltage spike greater than a predetermined clamping voltage, and
• a series regulator coupled in series between an input terminal and a corresponding output terminal, said series regulator including a transistor establishing an output voltage at the output terminals in response to an input control voltage provided by a voltage control circuit coupled across the input terminals in parallel with the shunt suppressor, said voltage control circuit comprising a transient suppressor component that shunts excess voltage so as to maintain the voltage supplied to the transistor at a constant level.

A spike prevention circuit adapted to be installed within a vending machine having a multi-drop bus supplying DC electrical power over first and second conductors and supplying communications data over a third conductor, said spike prevention circuit being adapted for installation along the multi-drop bus as a module and comprising:

• a pair of input terminals adapted to be coupled to the first and second conductors of a first segment of the multi-drop bus;
• a pair of output terminals adapted to be coupled to the first and second conductors of a second segment of the multi-drop bus to which a vending machine component is to be connected as a load;
• a shunt suppressor coupled across the input terminals, said shunt suppressor becoming conductive in response to appearance across the input terminals of a voltage spike greater than a predetermined clamping voltage;
• a series regulator coupled in series between an input terminal and a corresponding output terminal, said series regulator including a transistor establishing an output voltage across the output terminals in response to an input control voltage provided by a voltage control circuit coupled across the input terminals so as to be coupled between the first and second conductors of the multi-drop bus in parallel with the shunt suppressor, said voltage control circuit comprising a transient suppressor component that shunts excess voltage so as to maintain the voltage supplied to the transistor at a constant level;
• a first mating pair of bus connectors adapted for coupling the first and second conductors of a first segment of the multi-drop bus to the spike prevention circuit input terminals;
• and
• a second mating pair of bus connectors adapted for coupling the first and second conductors of a second segment of the multi-drop bus to the spike prevention circuit output terminals.