[TenTec] Orion and Heath SB-1000

[Dr. Gerald N. Johnson]

On Fri, 2007-04-06 at 15:54 -0400, Sinisa Hristov wrote:
> Measured data on SB1000 relay input:
> 
> open circuit voltage     = 12 V
> short circuit current    = 80 mA
> switch-off peaks        >= 230 V
> 
> Voltage and current are well within Orion output capabilities.
> However, switch-off peaks are unpleasant at best.
> 
> A 33 V Zener diode can be connected to Orion's AMP KEY output.
> Anode goes to ground and cathode (bar on the package) goes
> to the "hot terminal". This will limit peaks to 33 V.
> 
> This is safe, noiseless and fast.
> 
> 
> 73,
> 
> Sinisa YT1NT, VE3EA
> 
> _
An ordinary diode with the anode on the control line and cathode to +12
should clamp at a lower voltage, though the circulating current from
coil to diode will slow the relay fall out some. In some places with
solid state drivers that diode across the relay coil is always present.
With a fast driver transistor it wouldn't hurt if the diode or zener
were fast to turn on though a small capacitor can slow the voltage rise
to protect the transistor until the protective diode turns on.
-- 
73, Jerry, K0CQ,
All content copyright Dr. Gerald N. Johnson, electrical engineer