Designer's Corner 1251

Easy hinge assembly

Costs for attaching hinges to an enclosure door can sometimes outweigh the cost of the hinge itself. This slick new design cuts assembly cost to close to zero.

Ten-mm-diameter holes are punched in the door and enclosure prior to painting. Once paint is dry, hinge lugs placed through the holes accept a glass-reinforced nylon pin that clamps the hinge in place.

Hinge parts, usually arranged to provide lift-off capability, do not compromise security because the anti-vandal lugs prevent lift-off until the door is opened approximately 708. Other design features include positioning the hinge pivot such that a door can be opened 1808 even when the enclosure is placed immediately adjacent to a similar enclosure.

Kent Bellem, EMKA Inc.
1961 Fulling Mill Rd.
Middletown, PA 17057
(707) 986-1111.

Noise eliminator

The circuit splits the offending signal into a "straight" path that goes directly to the circuit's output amp and a "sidechain" path. A digital hum sampler in the sidechain path acquires a single full-cycle "snapshot" of the hum noise.

Potentiometers and an overload detector scale the hum signal to exploit the digital hum sampler's full-scale range. A phase-locked loop synchronizes the sampler to the ac power line.

After acquiring the hum sample, it's continuously "looped" to the output amp, but 1808 out-of-phase with the offending hum noise. Because the desired signal is never sampled, there are no phase cancellations or other audible side effects in the audio band.

Brian Stroehlein, Stro Lion Technologies Inc.
Box 300
Litchfield, CT 06759
(860) 567-0880.