Crossfire first gen with older hypertherm 350

[advmaker]

Some learning from today:

I sold my gen1 crossfire to a friend who has a older hypertherm 350. When we hooked everything up, we saw that the torch would fire but not turn off. Upon digging into it we figured that the older torch switch is a high current one which obviously that tiny reed relay (OMR-M-105H) can’t handle. I got a heavy duty solid state relay from amazon (https://www.amazon.com/gp/product/B01N0L5WSU/) and basically put a 9v battery on the input side where the circuit will be closed by the wires from crossfire control box.

Since the crossfire relay was fried, we took the risk of connecting the white and black wire that connected to the reed relay, to the bigger relay. To our delight it made the torch work!

Now we will just get the original relay and put it in place to not have to drive the big relay directly.

Attaching some pictures.

1. The crossfire reed relay that we need to replace
   

   

2. The heavy duty solid state relay from amazon driven by a 9v battery (3v will work too)
   

   

3. The circuit diagram for the big relay
   

   

4. First cuts (had to adjust pierce delay to 500ms as there is an initial delay before this torch fires)
   

   

[TomWS]

Good recovery!

The tricky thing with the OG relay is that it’s driven from 5V so most relays that have a 5V magnetic coil, are relatively high current to trip. The good news is that they do have a driver output to drive that signal so a relatively high current relay isn’t a huge risk. You just don’t want to go overboard with the size of the relay because you want it fast enough to trigger the plasma. The original relay was a reed relay which is very fast (by relay standards), but, as you found out, can’t handle a high current load.

If you want to get rid of the 9V battery, you can literally replace the old relay with the Solid State one, making sure you get the polarity of the control right. If you’re not sure, PM me and I’ll go back into the wayback machine and dig up the details on how you should hook it up.

[advmaker]

Thanks Tom for the insights.

I did think of just wiring the big relay inside the crossfire, then thought it is better to keep it stock by replacing the original relay so if my friend gets a new plasma later he can use it without needing the big relay.