Hickory and TT-4 Tool Setter wiring

[spumco]

According to the installation manual Hickory inputs can be sinking or sourcing depending on the input group/bank common pin.

I've designed my upcoming build to have sinking inputs (common = 0V) and sourcing switches/sensors (PNP), but have some uncertainty regarding the TT-4 tool setter.

The TT-4 tool setter schematic (for Acorn, S15087) shows it connected as a sinking (NPN) component, which would require the Hickory inputs to be configured as sourcing (PNP, common = 24v).

Can the TT-4 be configured as a sourcing component? Are there any internal components in the TT-4 (diodes, whatever) which would not work properly if I connected 24v to the TT-4 COM (black) wire?

Thanks

[centroid467]

According to the installation manual Hickory inputs can be sinking or sourcing depending on the input group/bank common pin.

I've designed my upcoming build to have sinking inputs (common = 0V) and sourcing switches/sensors (PNP), but have some uncertainty regarding the TT-4 tool setter.

The TT-4 tool setter schematic (for Acorn, S15087) shows it connected as a sinking (NPN) component, which would require the Hickory inputs to be configured as sourcing (PNP, common = 24v).

Can the TT-4 be configured as a sourcing component? Are there any internal components in the TT-4 (diodes, whatever) which would not work properly if I connected 24v to the TT-4 COM (black) wire?

Thanks

Good question!

I would suggest keeping the white wire at the highest potential and the black wire at the lowest. That is the correct polarity for the LED and associated circuitry.

Wiring would be:
* White to +24V
* Black to the input configured with COM=0V

The red and black wires are shorted inside the TT-4 so you may want to come up with an alternative arrangement for TT detection.

[spumco]

Thanks, that answers my question about the TT-4's internal scheme.

I'll just wire one Hickory input bank as PNP and leave the TT-4 as sinking/NPN so I don't have to outwit the detection feature.

In all your free time, an internal diagram of the TT-4 in the schematic/manual would be helpful for those of us who might want to 'color outside the lines' when it comes to wiring

[spumco]

And another thing...

Since I'm going to be wiring the Hickory input as PNP, is there any value to using 5V instead of 24V for the TT-4?

24V would provide better noise immunity... but I think this is unlikely to be an issue in an NC circuit.

5V would possibly give longer contact life... assuming the TT-4 is a standard kinematic switch arrangement.

Any thoughts?

[centroid467]

And another thing...

Since I'm going to be wiring the Hickory input as PNP, is there any value to using 5V instead of 24V for the TT-4?

24V would provide better noise immunity... but I think this is unlikely to be an issue in an NC circuit.

5V would possibly give longer contact life... assuming the TT-4 is a standard kinematic switch arrangement.

Any thoughts?

I don't see any advantage to using 5V for a TT-4. Yes, it is a standard kinematic switch but there is very little likelihood of any excess wear due to arcing or whatnot from using 24V.

[spumco]

Thanks again.

If there's no likely benefit, I'll keep it 24V. I hate having to manage a bunch of different signal voltages on a machine.