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WR-032-v2-2016-4-7.md

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New hardware revision WR-032 v2

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Recently (november 2016) I bought a couple of new STC-1000 devices and was amazed that, instead of the familiar WR-032 label, a new hardware revision was shipped. It was labeled WR-032 v2 with date 2016/4/7.

stc-1000-top
The top of the new STC-1000 device. Note that there's no label anymore!

The frontpanel does state WR-032 v2 but it seems that this is still the same as the original version. The microcontroller is still the STM8S003F3 device, so no changes here. Only the backplane shows some changes.

STC-1000
The backplane of the STC-1000 device with the new hardware revision

What has changed from the first WR-032 revision?

To start with, the new hardware revision is definitely NOT an improvement. No new features are added. The following things have changed:

  • The DC-DC converter chip (LNK567) has been replaced by another IC. This is not something to worry about: there's still 12VDC and 5VDC being made
  • The S3 output line is no longer wired to the terminal-blocks.
  • The 2nd temperature probe is now also wired to the terminal-block pin (pin 4) that we used as GND. This needs to be fixed if we still want PID-controlled SSR output.
  • Capacitor C9 is now populated (temperature conversion for 2nd temperature probe). This has no impact on the STC-1000p-STM8 firmware, since the ADC-input routine already deals with this.
  • Resistors R25 (S4 output), R26 (S1 output) and R27 (S2 output) are no longer populated. This is also not a problem.

What do we need to change?

  • The GND connection at the 5-pin terminal-block needs to be connected to GND again. It is now connected to the second temperature probe.
  • The S3 output needs to be connected to the SSR connection at the 5-pin terminal-block. This pin is now NOT connected.

What if I don't want to change anything?

  • You loose the slow-PWM PID-controlled SSR output.
  • A 5-pin terminal-block is no longer useful, since pin 4 is now connected to pin 1 (2nd temperature probe) and pin 5 is not connected. Solder a 3-pin terminal block in place, so you can still connect a 2nd temperature probe.

All other functionality will remain intact. So you can still have 2 temperature probes. Up to you to decide if you need to make the hardware changes.

Ok, what do I need to change?

To get the same functionality as with the original WR-032 hardware (in combination with the STC-1000p-STM8 firmware of-course), you need to prepare the connectors the same way you did with the original version:

  • Remove the 2-pin terminal-block for the temperature sensor.
  • Replace it with a 5-pin terminal-block with a pitch of 5 mm.

Then, proceed with the following:

  • Cut the 2 wires going to and from pin-4 of the 5-pin terminal block. Cut where the red lines are in the picture. This pin is now completely isolated from anything else. Measure with a multimeter!
  • Solder a wire between pin 1 of the 5-pin terminal block to the S1 solder-pad. This is the yellow line in the picture. Now the 2nd temperature probe is connected again with the original line.
  • Solder the now isolated pin-4 of the 5-pin terminal block to the GND connection of the 470 µF/25V capacitor. This is the black line in the picture.
  • Solder pin 5 of the 5-pin terminal-block to pin 5 of the frontpanel connector. This is the S3-output line and the blue line in the picture.

STC-1000
The backplane of the STC-1000 device with the proposed changes

Now you have the same functionality again as with the standard WR-032 hardware revision.

wr032-v2-changes
This is how it looks when the changes have been made