Random arc signal lost

But mount these resistors proud of the circuit board for heat dissipation. They will get hot!

if you are punting two in series then I think they would only dissipate half the power in each so would not get hot

I was recently informed that one of the developers has created a new debounce component that behaves like a "normal" HAL component in that it can have multiple instances that are named and it is amenable to Twopass processing. I have tested it out and I think it is much easier to use than the existing so I am going to use that for new configurations. Each of the input signals will have its own independant debounce component so the delay can be adjusted individually. Preliminary documentation is here

To complete this thread, the jury is back with a decision on the pull down resistance required to exceed the minimum current through the Hypertherm dry contacts if you are using Plasmac Mode 1.

Recapping, the 7i96 inputs draw about 5 mA and the 7i76e inputs draw 1 mA. The minimum current required on Hypertherm and Everlast machines is 100 mA. These low currents can (and have) caused oxidisation of the dry contacts which in time can cause intermittent performance (and eventually total failure) of the ArcOK signal. This is a very frustrating issue if (or when) it occurs.

Assuming 24v field power, the recommended solution is to place 3 x 270 ohm 5 watt resistors in parallel which will give 90 ohms resistance with 15 watts of power dissipation ability between the ArcOK input pin and field power ground. This will ensure 267 mA passes through the dry contacts with 6.4 watts of power to dissipate so there is plenty of headroom. Make sure there is an air gap between the resistors and any surrounding object that could melt.

Aussies can purchase Jaycar part No RR3284 at the cost of AUD 68 cents each.

The jury also noted that the Hypertherm relay used for ArcOK takes 10 ms to turn on and 4 ms to turn off so it is unlikely that debouncing will be required.

Big thanks to Snowgoer, the chief test pilot for going above and beyond again by dismantling his machine to locate and identify the relay used.

I would recommend anybody using mode 1 on any machine to adopt this modifications. When I think of it, there have been a few reports of people having arcOK issues with mode 1.

rodw wrote:

The jury also noted that the Hypertherm relay used for ArcOK takes 10 ms to turn on and 4 ms to turn off so it is unlikely that debouncing will be required.

Could the jury explain how this works, it doesn't seem to gel with data from relay manufacturers.

snowgoer540 wrote:

This, among other reasons, is why I'm not doing it.

I read your relay data sheet as a minimum load, so to me that would mean if they say 100ma@5V that equates to 0.5W so at 24V you would need a 1K2 resistor giving you a 0.5W load, if you wanted to do that as well as the debounce. Protected two ways...

tommylight wrote:

rodw wrote:

Assuming 24v field power, the recommended solution is to place 3 x 270 ohm 5 watt resistors in parallel which will give 90 ohms resistance with 15 watts of power dissipation ability between the ArcOK input pin and field power ground.

That should be in series.
Parallel that would end up at 9 Ohm and draw over 2 Amps.

Sorry my typo. 3 x 270 ohm resistors in parallel . Corrected and you can review the link to aycar to confirm.