Is RAMPS bed control proportional or BangBang?

I have an external controller maintaining temp to my heated bed, heated by a 110V silicone pad I had lying around. I bought a solid state relay (12V dc controlling 110V AC) and wanted to control the bed through the RAMPS 1.4 controller. But I can't find anywhere where it says if the controller for beds are bangbang or proportional. If proportional, won't work on my new relay. Running splinter firmware

it is pwm controlled.

you're aware that bang-bang refers to the style of the control loop, rather than the output method *(for instance, a PID control loop can be executed using a true analog or pwm output, depending on whether the controller has a D/A output or a simple binary out (on off).

Thank you for the information, I hadn't realized I was using the terminology incorrectly.

Your information about PID loops, while interesting, unfortunately does not tell me what I need to know. What changes in firmware/software/hardware do I need to complete in order for my on/off solid state relay, controlling 110v, controlled by the RAMPS 1.4 board with, I assume, 12 v output.

My relay is a Grayhill 70S2-03-C-25-S unit, rated for 3 to 30 v dc input, 24 to 280v output, but does not control proportionally. I just need 12 v on or off to control my heated bed. Any ideas? Has anyone else controlled a heated bed using a relay? Can you tell splinter firmware in a RAMPS board to control the heated bed with an on/off type signal, properly buffered? Do I need to tell it +- how many degrees?

I use Marlin with RAMPS, but Marlin is based on Sprinter. I use an AC heated bed with a solid state relay. It is on-off controlled. The output can be PWM'd, but for heated bed control it is just full on (12V) or full off (0V).

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Thank you, that is good to know. Once I tweek a few other problems I am having (lock-ups and the sort) I am going to simplify my instrument, get rid of external temp control and use the relay. Thanks for the feedback. Did you have to configure Marlin to tell it to output that way?

It has bang-bang control at full-on-off by default. I think this was intentional so that it can operate properly with relays, whether mechanical or solid state.

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Idaholion, oops, my bad... I was responding to michel pet. PWM can be used to provide PID or bangbang through a relay. As far as I know, at least in marlin (new to this myself and am just going through the various files) one can choose either method. I'm not sure what the default is on the firmware in your board, but on the marlin pre-installed on my printrboard it appears to be set to PID control by default.

i don't think relays will work that well with pwm by default. unless someone has implemented my software version of pwm. bang band is ok for heated bed. temp is not as critical as it is for nozzle.

jamesdanielv Wrote:
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> i don't think relays will work that well with pwm
> by default. unless someone has implemented my
> software version of pwm. bang band is ok for
> heated bed. temp is not as critical as it is for
> nozzle.

Relays will not work properly with pwm, the exception being solid-state relays that are intended for that purpose. Bang-bang control of the heated bed works well because of the large thermal mass of the heated bed in comparison to the power it draws.

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As NewPerfection noted, many SSRs are suitable for use with PID control that uses PWM output. I've used them as far back as the early 1990s for PID based temp control (my own design, driven by content from a small single board not unlike the Arduino in some ways) and as recently as 2007 for PID based fuel servo control (a commercial, pneumatic interstage bellows drive a customer asked us to incorporate into a fuel test stand)

In fact, there are probably even several electromechanical relays I could use to make a functioning PWM output for PID controller.

Solid state yes. But with experience not a standard relay for pwm.
You could modify the Pwm speed and slow it down. Pid function will be useless otherwise. In bang bang mode relays are fine.

Hello, this seems like the best place to ask this question

I have a YH185B relay (PDF)
I guess I can not use this relay to control my QU-BD 15 amp silicone heatpad? (here)

They claim it can be run dirrectly off the Ramps 1.4 board... but?....
I'd like to run it directly from the board, but if I need a relay,
can someone point me in the right direction please?

Thanks!
Chris

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Custom all metal CoreXY
- Duet 2 Wifi w/ PanelDue 7i
- 330mm x 360mm x 500mm
- 750w Silicon heater

Custom Mendel90
(Backup printer - Old reliable!) - Sold

Just don't enable PID for heater bed. I think it is disabled by default for heated bed/and may not even exist for heated bed. Also max power settings should be set to 255, to disable pwm.

Post your config and adv config files and someone will let you know for sure.

okay thanks James

I have not got into the software side of things yet, just getting things wired up now.
The firmware I will be using is Marlin RC2. I have made no changes to what was downloaded. (GitHub)

So much to learn!!
Its Awesome!

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--------------------------------------------------------
Custom all metal CoreXY
- Duet 2 Wifi w/ PanelDue 7i
- 330mm x 360mm x 500mm
- 750w Silicon heater

Custom Mendel90
(Backup printer - Old reliable!) - Sold