392 Chapter 13
normal. Continuous power must be furnished to this
timer, as shown in Fig. 13-26D.
Interval. Upon application of the control power, the
output switch operates. At the end of the time-delay
period, the output switch returns to normal. Control
power must be interrupted in order to recycle, as shown
in Fig. 13-26E.
Momentary Actuation. Upon closure of the control
switch, the output switch operates, and the time-delay
period begins. The time-delay period is not affected by
duration of the control switch closure. At the end of the
time-delay period, the output switch returns to normal.
Continuous power must be furnished to this timer, as
shown in Fig. 13-26F.
Programmable Time-Delay Relay. Programmable
time-delay relays are available where the time and func-
tions can be programmed by the user. The Magnecraft
W211PROGX-1 relay in Fig. 13-27 is an example of
this type. It plugs into an octal socket, has ±0.1%
repeatability and four input voltage ranges. It has four
programmable functions, On Delay, Off Delay, One
Shot, and On Delay and Off Delay. There are 62
programmable timing ranges from 0.1 s to 120 min and
the relay has 10 A DPDT contacts. An eight position
DIP switch is used to program the timing function and a
calibrated knob is used to set the timing.References
- Logan Hedin, TenHex and Gary Arnold, Thermal Design of an LED Commercial Florescent Tube, Cool Poly-
mers; Presented at IMAPs New England 2008 35th Symposium. - Solver-Calc©, An Excel Spreadsheet Program for Rapid Thermal Management Calculations, by Villaume Asso-
ciates, LLC, http://www.thermalseminars.com. - Heat pipes have become increasingly useful in spreading heat loads and moving heat to an area where the con-
vective fin surface area may be more effectively positioned in the available air flow path. “Google” for vendors
as there are quite a few suppliers of this component in a thermal solution. - TPG is a product designator for highly oriented pyrolytic graphite offered by Momentive Performance Materials
in Ohio. The in plane thermal conductivity is ~1750 W/m°K. It can perform in high watt density (> 80 W/in²)
applications without suffering “burn-out” failures that are possible with regular heat pipes. - Two major suppliers; Wakefield Thermal Solutions, Pelham, N.H., and Cool Options Inc., Warwick, R.I.
- Designer’s Handbook and Catalog of Reed and Mercury Wetted Contact Relays, Chicago: Magnecraft Electric Co.
- “Relays, Solenoids, Timers, and Motors,” Electronic Buyer's Handbook, 1978. Copyright 1978 by CMP Publica-
tions. Reprinted with permission. - “Relay Loads” Electronic Design 26, December 20, 1978.
- Solid-State Relays, Chicago: Magnecraft Electric Co.
- Designer's Handbook and Catalog of Time-Delay Relays, Chicago: Magnecraft Electric Co.
- Coto Technology Reed Relays and Dry Reed Switches, Coto Technology.
Figure 13-27. A programmable time delay relay. Courtesy
Magnecraft Electric Co.