Has anyone got one?

[Tony]

Can you use a 40A R/C electronic speed controller (ESC)?  They are designed to drive a lot of current from a PWM signal.

[Tony]

edit:

I googled it, you should be able to set the ramps board to bang-bang instead of PWM for hot bed control


which means it powers the bed output either full on or full off

so then you could use a 12v car relay, which might be easier ?

mosfet would give better temperature control, but with a bigger bed it will have less of an effect, and +/- 2 or 3'C shouldn't make a difference ?

Cheers, I'll have a look at that.

There goes my lack of knowledge about things electrionical, bang-bang, logical but what does PWM mean?

Pulse Width Modulation, shamelessly stolen image here:



100% duty cycle is always on.  Imagine dimming your household lights by switching them on and off very, very fast.

[Julian]

Pulse Width Modulation ... even I know that! EDIT ... Tony beat me to it!

Had a thought this morning ... as this is a lash up printer, what's the need to drive the heated bed from RAMP and Marlin?

It only has to be switched on at the start of a print and off part way through or at the end.  So why not use a little Willhi or similar on, off temperature controller in combination with Kinghtys great suggestion of a car relay.

A quick and simple fix ...  about £6 quid from china and about £12 - 13 from the UK ... or I've got a brand new 220v one you can borrow.

[Tony]

You and your la-de-dah electronically heated bed.  I have to light a fire under mine, that's how it was back in them olden days.

[Jamesrl]

You and your la-de-dah electronically heated bed.  I have to light a fire under mine, that's how it was back in them olden days.

You don't have to tell me about the old days,  I was there.

[Jamesrl]

So why not use a little Willhi or similar.

There y'go again and I'd hate to think what would hit my screen if I googled "little wilhi".

[therecklessengineer]

So you're saying an AC/DC ssr will work ok with DC/DC, would I be right by switching the + and direct wire the -

I have a 30a 12v supply ready for it, just need a relay.

Yup. Wire up the trigger side as normal. Polarity won't matter on the load side - whichever way around you like. It'll switch on/off just like normal.

[Jamesrl]

Thanks for that.