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[eightbits]

I recently had to replace an older X10 transceiver (from Radio Shack) with a TM751.
I am using the the TM751 outlet to control a lamp using a screw in fluorescent bulb.
When turned off the bulb will flicker on about once or twice per second.

The original module never had this problem. I also purchased a AM466 and it also doesn't exhibit the problem. I understand that the appliance version (AM466 is designed to work with  fluorescent bulb's. But , because the doc's did not mention this as a problem with the TM751 and
the fact that the older module (over 6 years old) did not have any problems , I am surprised with this issue.

In the new TM751 module when turning off , the relay sounds real weak.

I am going to assume that it used a relay because of the ON/OFF sounds. I know that a solid state relay or TRIAC based designs can leak current. But, I did not think this be the case because of hearing the sound of a relay clicking on and off.

Do I have a defective TM751?

BTW, first post here.

Thanks.

[dhouston]

Do I have a defective TM751?

No, both the TM751 & RR501 have a circuit to detect the state of the relay. It leaks a bit of current through the outlet and that's what causes what you see. Here's a schematic of the RR501 - The TM751 relay circuit is similar.

• http://www.idobartana.com/hakb/RR501_Schematic_vH.pdf

[eightbits]

  Thanks a million for the reply and the schematic. I didn't think about the circuit monitoring the
state of the relay. Wonder why it didn't just monitor the coil?

I didn't understand why the older radio shack transceiver worked without the blinking.

I will take a look in detail the schematic. I notice the PIC ship was used,
I am a Atmel AVR freak

I think I will just order an additional appliance type module and move the TM751 to another location and use another appliance module to control the lamp.

Once again, thanks for the quick and complete reply.

Cheers.

[dhouston]

It's a latching relay.

[eightbits]

So, it must be that the older Radio Shack version did not have a 'latching relay'.
Looking at the schematic , looks like the 'latching' is accomplished by the SCR that fires the relay.
I am thinking that by latching the relay, there is no reason to dedicate a pin of the micro to
keep the state of the drive to the relay coil.

This was far more than I originally wanted to get involved, but it is interesting how things work.

The X10 scheme seems to be pretty reliable, so I will just purchase a couple more of the
appliance modules and change where I plug in the TM751.

Great forum 

Cheers