Control for activating motor vehicle electrical load

• US 3,909,619 A
• Filed: 05/17/1974
• Issued: 09/30/1975
• Est. Priority Date: 05/17/1974
• Status: Expired due to Term

• Current Assignee: Jerrold L. Mullen, Larry L. Colville, Richard A. Kniesly
• Original Assignee: Jerrold L. Mullen, Larry L. Colville, Richard A. Kniesly
• Inventors: Kniesly, Richard A., Colville, Larry L., Mullen, Jerrold L.
• Primary Examiner(s): Hohauser, Herman J.
• Application Number:
  US05/470,971
• Time in Patent Office: 501 Days
• Field of Search: 307/1R,1LS 315/83,82,77 340/62 180/105
• US Class Current: 307/10.8
• CPC Class Codes: B60Q 1/143 combined with another condition, e.g. using vehicle recognition from camera images or activation of wipers
• CPC Class Codes: B60Q 2300/112 Vehicle speed
• CPC Class Codes: B60Q 2300/312 Adverse weather
• CPC Class Codes: B60Q 2300/314 Ambient light

Abstract

A control for activating an electrical load, such as a lighting system, in a motor vehicle having an ignition system. A first voltage, inversely proportional to the frequency of the motor vehicle ignition pulses, is applied to the anode of a programmable unijunction transistor (PUT), and a fixed reference voltage is applied to the gate of the PUT. At low engine speeds, the PUT tends to conduct periodically, deactivating a relay which is operable to energize the motor vehicle headlights. At higher engine speeds, with a greater frequency of ignition pulses, the programmable unijunction transistor fires less frequently, or not at all, allowing the energization of the headlight relay and hence, the application of power to the headlights. Circuitry is also provided to energize the motor vehicle headlights, taillights and instrument lights in response to the activation of the motor vehicle windshield wiper motor and also in response to ambient darkness.

Claims

1. A control for coupling electrical power to an electrical load circuit in a motor vehicle having an ignition system comprising:

a motor vehicle electrical load circuit;

control means for coupling electrical power to the load circuit when the control means is energized;

ignition circuit means, having an input coupled to ignition pulses in the ignition system of the motor vehicle, for producing at an output a first electrical signal dependent upon the frequency of the ignition pulses;

reference circuit means for producing at an output a reference electrical signal; and

comparison circuit means, having a first input coupled to the output of the ignition circuit means and having a second input coupled to the output of the reference circuit means, for energizing the control means when the first electrical signal differs from the reference electrical signal by a predetermined amount.

2. The control of claim 1 in which the comparison circuit means includes a programmable unijunction transistor whose anode is coupled to the output of the ignition circuit means and whose gate is coupled to the output of the reference circuit means.

3. The control of claim 1 in which the motor vehicle electrical load circuit is a lighting circuit.

4. The control of claim 3 in which the compArison circuit means includes a programmable unijunction transistor.

5. The control of claim 4 in which the anode of the programmable unijunction transistor is coupled to the output of the ignition circuit means, and the gate of the programmable unijunction transistor is coupled to the output of the reference circuit means, and in which the comparison circuit means further includes transistor switching means, having an input coupled to the cathode of the programmable unijunction transistor, for energizing the control means in the absence of conduction by the programmable unijunction transistor.

6. The control of claim 5 in which the control means includes a first relay having a coil and the transistor switching means includes a first capacitor coupled to the motor vehicle electrical power source and a first NPN transistor coupled in parallel with the first capacitor at its collector and emitter terminals, the base of the first transistor being coupled to the cathode of the programmable unijunction transistor, whereby the first capacitor is discharged when the first transistor is activated by conduction of the programmable unijunction transistor.

7. The control of claim 6 in which the transistor switching means further includes a series of transistor switches operable to be gated on when the charge on the first capacitor exceeds a predetermined amount, the series of transistor switches including a final transistor switch in series with the coil of the first relay.

8. The control of claim 7 in which the ignition circuit means includes a capacitor charging through a variable resistance, the positive terminal of the capacitor being coupled to the anode of the programmable unijunction transistor and also to the collector of an NPN transistor whose emitter is coupled to ground and whose base is coupled to the ignition pulses of the motor vehicle.

9. The control of claim 8 in which a resistor is coupled between the side of the relay coil which is at lower potential and the higher potential side of the capacitor of the ignition circuit means.

10. The control of claim 1, in which the control means includes an input through which the control means may be energized, and further comprising a windshield wiper motor having a first terminal which is energized by the motor vehicle power source when the windshield wiper motor is in operation, the first terminal of the windshield wiper motor being coupled to the input of the control means.

11. The control of claim 10 which further comprises:

photosensitive means for producing an electrical signal dependent upon the level of ambient light of the motor vehicle; and

electronic switching means for energizing the control means when the electrical signal from the photosensitive means exceeds a certain value.

12. The control of claim 11 in which the photosensitive means includes a photocell and the reference circuit means includes a variable resistor, and further comprising:

means for preventing energization of the control means, including a master control switch; and

and indicator lamp coupled to the electrical lighting circuit at a point which is energized by the motor vehicle electrical power source when the lighting circuit is energized.

13. The control of claim 12 which further comprises:

a housing mounted on the dashboard of the motor vehicle, the photocell, variable resistor, indicator lamp and master control switch being mounted in externally accessible locations in the housing;

a light shield slidably mounted within the housing and operable to be moved over the photocell, shielding the photocell from ambient light; and

electrical conductor means for coupling elements in the housing to the remainder of the control circuitry.