Print hammer drive circuit with compensation for voltage variation
First Claim
1. A control circuit for a solenoid for controlling the application of a current of a preselected magnitude to the coil of the solenoid for a preselected time, said circuit comprising:
- a current source selectively connected to said coil;
means for connecting said current source to said coil; and
means for interrupting current to said coil a predetermined time after said current in said coil has reached a predetermined level;
said interrupting means including a current sensor for sensing said predetermined level, a current reference source and a comparator connected to both said current sensor and said current reference source.
0 Assignments
0 Petitions
Accused Products
Abstract
A print hammer drive circuit is driven by a voltage supply having inherent voltage variations. The driving current is applied to the print hammer coil and the level of the current in the coil detected. After the level of the current in the coil reaches a predetermined maximum level a timing circuit is initiated to control the duration of application of maximum current. Variations in supply voltage on the duration and force of strike of the print hammer have greatly reduced since all timing is based relative to the time that the predetermined drive current level is achieved as distinguished from timing which includes the rise time of the driving current wave form. Also the effects of variations in inductance from coil to coil can be compensated for by adjustment of the timing circuit.
37 Citations
2 Claims
-
1. A control circuit for a solenoid for controlling the application of a current of a preselected magnitude to the coil of the solenoid for a preselected time, said circuit comprising:
-
a current source selectively connected to said coil; means for connecting said current source to said coil; and means for interrupting current to said coil a predetermined time after said current in said coil has reached a predetermined level; said interrupting means including a current sensor for sensing said predetermined level, a current reference source and a comparator connected to both said current sensor and said current reference source. - View Dependent Claims (2)
-
Specification