Cotrol peltier as cold bed

Projects Programming
1

Hello. I'm trying to build bio3d printer. I need cold bed for printing bed. I use marlin code. and Peltier for cooling. I attached Peltier pins where define for heatbed pins.

The problem is i cant control temperature. Help me to control bed in clod temperature.???????????

2

We're missing a lot of detail.

3

Have a look at the forum guidelines. They give useful information about how to write a post so that you will get a resolution to your problem. You need things such as a schematic, code in code tags and description of what is and is not happening compared to what you want to happen.

4

You will have to invert the sense of the heater output. Marlin is going to try to put more power into the Peltier when it wants to INCREASE the temperature. You want to reverse that. One way is to have the heater output switch a relay and have the relay turn power to the Peltier ON when the relay is OFF.

5

i solved my problem by inverting the BED_LIMIT_SWITCHING logic.

is it possible to do the same with PIDTEMPBED logic?

6

any idea?

7

aliy97:
any idea?

Could you give more information please? that way we could help you.
for us, it's just like jumping in the middle of a conversation so we have missed a lot of details.

8

sebasdt1:
Could you give more information please? that way we could help you.
for us, it's just like jumping in the middle of a conversation so we have missed a lot of details.

I want to use Peltier as heated. but I use the cold side of Peltier because I need low temperatures for my bed( around 10 celsius). so I inverted the logic in codes (BED_LIMIT_SWITCHING) and it works. but I want to control my bed temp with PIDTEMPBED logic. (codes are in temperature.cpp)
is it possible to invert PIDTEMPBED logic?

9

In Temperature.cpp: float Temperature::get_pid_output_bed() {

Change the last line from:

    return pid_output;

to

    return MAX_BED_POWER - pid_output;
10

johnwasser:
In Temperature.cpp: float Temperature::get_pid_output_bed() {

Change the last line from:

    return pid_output;

to

    return MAX_BED_POWER - pid_output;

thanks, it worked.
and another question. when I plug in my source the Peltier(heatbed) works automatically, is it normal?.... is it possible to set codes that Peltier(heatbed) works when I command with repetier?
I got errors that say it doesn't work when both are enabled.

11

aliy97:
when I plug in my source the Peltier(heatbed) works automatically, is it normal?

It's normal if the default temperature is set to 0 and the room temperature is, say, 25. The Output of the PID will be zero which gets inverted to MAX_BED_POWER. Maybe you can configure the initial temperature to something above room temperature, like 30 or 40. I don't know where to do that but I expect you will have to change the code somewhere. It's doesn't seem like the kind of thing where they would ever expect zero to not be the right value.

12

johnwasser:
In Temperature.cpp: float Temperature::get_pid_output_bed() {

Change the last line from:

    return pid_output;

to

    return MAX_BED_POWER - pid_output;

sorry, actually it doesn't work. but I solved my problem by editing

pid_error_bed = target_temperature_bed - current_temperature_bed;
to below

pid_error_bed = current_temperature_bed - target_temperature_bed;

thanks, for your support and help.