Valve Driver Power Leakage

BrainScientist

Hi,

We have been using a number of Valve Driver modules for a few years now, with State Machine 2. Recently, we accidentally figured out that a couple of modules show 18-19V running in the circuit when the valve is closed, and 24V when open. For example, in one module, valves 1, 3, 4 and 8 show 0V when the circuit is supposedly closed, and 24V when open - that's what I expected. However, circuits for valves 2, 5, 6, and 7 show 19v even when those circuits (and all others) are closed, but 24V in the open channel when it is opened. The pattern holds if the VM is disconnected from the State Machine, but the valve module power supply is left connected.

Now, we wonder, are those modules fried? The Module seems to be otherwise functional in terms of being operable, but obviously running 19 V through a valve all the time doesn't seem to be a good thing.

Related: what's the recommended power supply specifications, for using 24V valves with the ValveModule? Based on specs on the Valve Module page ("12-24V; >1.5A"), we have been using a 24V, 3A power supply. Is that OK?

The guidance is confusing, since the recommended power supply seems adequate to power 12V valves, but not 24V valves.

Any help would be appreciated,
Thanks, Avinash

Josh

Hello Avinash,

Definitely an odd bug! A few questions to help debug:

-What valves are you using (manufacturer part#)?
-To measure the valve voltage, which multimeter are you using, and where are you connecting the probes?
-If you set the multimeter to read current and put it in series with the valve on one of the symptomatic channels, what current do you read when the valve is open and closed?
-Do the bodies of the valves on channels 2, 5, 6, 7 dissipate noticeably more heat when closed vs. the valves on Ch1, 3, 4, 8?

The valves are driven by Infineon ISO1H815GAUMA1, a high side driver IC with integrated circuitry to directly drive inductive loads. The chip is rated for up to 1.5A per channel. The choice of power supply should be informed by the specs of the valves you're driving. Valve datasheets will usually specify the peak current draw that occurs transiently when valves first open.

-Josh