TV channel
audio receiver
Is there a dedicated chip that would produce the audio from TV channels. I wish to construct a Walkman-type unit to receive the TV channels if possible.
(B. A., via email).
The most direct approach would be to adapt the tuner, IF and sound stages from a VCR. We don’t know of any chipset that would do the job.
4-channel lighting
desk/dimmer
In the 4-Channel Lighting Desk/Dimmer article (June/July, 1991), you specify 4 x Teccor Q6040J7 40A 600V insulated tab Triacs from NSD. Do you know where I can get these or an equivalent device?
(A. W., via email).
The Triacs are 40A 600V insulated tab types in the TO-218 package. The BTA41-600B is a suitable replacement and is available from Farnell Electronic Components at www.farnellinone.com.au – phone 1300 361 005. The part number is 505-778 and the cost is $20.99 each plus 10% GST plus delivery.
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Fan cooling
does not work
I built the thermostatic switch for car radiator fans some years ago from the March 1992 edition of SILICON CHIP. It works as advertised. Can you advise what the approximate current draw should be for the control circuit? The reason that I wish to know is that I have the unit wired direct from the battery so as to provide cooling when the engine is turned off.(F. W., Airport West, Vic).
The circuit will draw around 100mA on standby so it is not suitable for permanent connection to the battery. Perhaps a thermostat switch (eg, Jaycar ST-3836) that closes at 100°C and reopens at around 85°C could be used to switch a relay and drive the fan for the purpose of running when the ignition is off. In this way the current would be zero when the thermostat is off.
Note that running the radiator fan when the engine is off does not help cool the engine since the coolant is not flowing. If you want to do that (and we cannot see why it’s worth doing), you would need an auxiliary electric-powered water pump to circulate the fluid while the fans are running.
