reTerminal-DM touchscreen unstable when powered from industrial 24 V supply, works only when touching chassis

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1

I am using a reTerminal DM with injection molding machine and facing unstable capacitive touch behavior.

Symptoms:

  • Screen randomly zooms in/out

  • Touch position shifts

  • Touch becomes stable only when I physically touch the reTerminal chassis with my hand

  • Issue appears when powered from Mean Well mdr-60-24 power supply.

This suggests a grounding or common-mode noise issue affecting the capacitive touch controller.

Power setup

Power supply used:

Mean Well MDR-60-24 (DIN-rail SMPS)

Connections made:

  • L/N connected to machine single-phase supply

  • +24 V / −24 V connected to reTerminal DM

  • V− bonded to panel PE

  • reTerminal chassis bonded to panel PE

  • MDR-60-24 FG bonded to panel PE

Despite these connections, issue persists.

Measurements

Measured AC voltage between:

MDR-60-24 V− and panel PE ≈ 60 V AC (before grounding changes)

After bonding FG and V− to PE, behavior improved slightly but touchscreen instability still remains.

Touch becomes stable immediately when:

I touch chassis with my hand

which suggests missing reference stabilization or high common-mode noise in cabinet environment.

Machine environment

Installation is inside an injection molding machine panel containing:

  • hydraulic motor contactors

  • possible VFD drives

Cable length between PSU and reTerminal is short (<2 m).

Tests already performed

Tested:

  • bonding V− to PE

  • bonding FG to PE

  • bonding chassis to PE

  • verifying continuity of panel earth

Questions

  1. Is reTerminal DM known to require isolated supply in industrial control panels?

  2. Does Seeed recommend grounding output negative to PE or keeping it floating?

  3. Are there any official EMC mitigation guidelines for capacitive touch stability in noisy cabinets?

  4. Has anyone successfully deployed reTerminal DM with injection molding or CNC panels without isolated DC-DC stage?

2

Hi there,

SO, on the IO/ panel isn’t there an ISO/GND pin , used on the canbus often too.
it’s the dedicated isolated pin on the reTerminal, I was under the impression. I think also a post of another maker using it similar too , the isolation for power supply GND (noise) issue for your use case FAIK.

HTH
GL :slight_smile: PJ :v:

3

Hi @PJ_Glasso

I tried following connection: Injection Molding panel earth to Negative of the meanwell MDR-60-24 power supply output and ran a short wire to connect panel earth to reterminal-dm earth [Above the power supply port]

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As per your suggestion, should I connect injection molding machine panel earth to GND_ISO?

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Because this earthing issue is causing touch screen instability [zoom in/out, ghost touch] and is not usable at all. Should I also reach out to seeedstudio team for the same?

1 Like
4

Hi there,

Ok, YES absolutly . Connect it and report back, You can’t hurt anything so no worries there.
if possible can you measure your power supply AC ripple component. if it’s too noisy , find a higher working voltage CAP and nothing huge 20 uf. see if it lowers it a bit in the meter, (ac settings) checking the DC supply. note the reading, add the cap ..note the reading. Any change if so try the reTerminal again.

HTH
GL :slight_smile: PJ :v:

I have had some super crazy noise enviro’s before, one was a motor for an overhead crane… when that thing kicked into gear and moved , it would spike the AC around the whole neighborhood it seemed :grin: We added Heavy Isolation and split filtered the mains supplied to it. added some additional CAPs to the power supply for the servos and MMI display power legs, and life was good again. :crossed_swords: