Heatbed will not heat

I have a Prusa i3 printer. Been using it for about 8 months with PLA filament. Works great. I decided to try ABS filament. The problem is the heatbed will not heatup, It will start to heatup and just go to 23 deg. The bed is a, PCB heatbed Mk2a. Using anduino frimware. Is there something in the firmware that has to be changed?

Ed

Edited 1 time(s). Last edit at 03/04/2015 10:52AM by tobig11.

Did you ever heated up the bed for PLA?
Looks like is not getting power from the board. Check voltage going out to bed.
Is the LED lighting up solid or blinking?

It could be several things, from a bad mosfet, bad wiring connection or settings in firmware.

There is no voltage at all at the anduino board hookups.
Ed

Dead mosfet, or wrong printer type in firmware.

Does the heatbed have to be turned on in the firmware? If so, Hw do you do this?
Arduino board. Firmware is; Reprap firmware based on Sprinter and grbl.
All the red led comes on solid then goes out.

Edited 1 time(s). Last edit at 03/05/2015 10:11AM by tobig11.

No, you don't have to turn it on or off in the firmware, but if the printer didn't came with it and you install one, you have to set the correct values in the firmware. If you install it and didn't add the thermistor to configuration h file, then the board will not recognize the info coming in from it, also the power setting in the PID might be too small for that bed? Change it to full 255 and see what happens.

If your configuration h look like this:
#define TEMP_SENSOR_0 57
#define TEMP_SENSOR_1 0
#define TEMP_SENSOR_2 0
#define TEMP_SENSOR_BED 0

Sensor "bed" is 0 which means: no sensor.

// This sets the max power delived to the bed, and replaces the HEATER_BED_DUTY_CYCLE_DIVIDER option.
// all forms of bed control obey this (PID, bang-bang, bang-bang with hysteresis)
// setting this to anything other than 256 enables a form of PWM to the bed just like HEATER_BED_DUTY_CYCLE_DIVIDER did,
// so you shouldn't use it unless you are OK with PWM on your bed. (see the comment on enabling PIDTEMPBED)
#define MAX_BED_POWER 256 // limits duty cycle to bed; 256=full current

The last define here is 256 for the bed, if yours is less, changed to full and test.

If your configuration h looks good, then is definitely a dead mosfet. But don't worry, they are cheap and easy to change.

You mentioned Grbl but prusa come usually with marlin? Basic Grbl is more for CNC than 3d printers, and will need some modifications to accept a bed "thats what marlin is". Are you sure you are using plain Grbl? If so, that would explain your bed not working.

Edited 2 time(s). Last edit at 03/05/2015 11:51AM by ggherbaz.

It is marlin, but it also said Sprinter & grbl

ok, the check your configuration h file and if right one last check that you can do is to test voltage at mosfet, if voltage is present at Vcc pin at the mosfet but nothing is coming out, the mosfet is dead.

The firmware seems alright, except for the first #define TEMP SENSOR you say to set it at 0 57. I have no 57. The voltage at D8 is one volt and the heatbed will heat to 21 deg. no higher. I read that you can turn the voltage up on D8 somehow at the power supply. If so how do you do that? I working with 120 V power.
If you still thing it is the mosfet, what kind should I get. My boad is anduino. The led light goes on for a short time solid then goes out.
Ed

Edited 1 time(s). Last edit at 03/10/2015 11:07AM by tobig11.

That was an example, the 57 was just a number, you will have to put the right number for your thermistor.

If Max bed power is set to 256 like in the example I posted before, you should have full cycle at mosfet (12 bolts constant).

The 1 volt you mentioned it's at what pin of your mosfet? Also when you refer 120 volts, I assume is at your power supply, but what is the wattage of the 12 volts supply? You need minimum of 300 watts to be able to powered the bed (9 amps) if your power supply is underpowered (less than 10 amps output) most likely it will get hot and shut down on you when you try to power the bed. But assuming you purchased the printer as a kit, it should have a capable power supply.

The one volt part it's where most likely your problem is, like I said, at both pins 1 and 2 you should have 12 volts with D8 + on pin 1 when off and on pin 2 when on, disconnect the bed from the board and check again the voltage. If still at 1 volt at output pin your mosfet is damaged, if the 1 volt is at pin 1 or input pin then there is something wrong with your board. If you get 12 volts without the bed then is your bed the one with problems.

Edited 3 time(s). Last edit at 03/11/2015 11:59AM by ggherbaz.

[reprap.org]

Look at this schematic and it will give you hopefully a better understanding. If you measure voltage from + of your D8 connector to ground on the board, you should have 12 volts, when the mostfet receives the signal (probably the 1 volt you mention) it opens the ground path to - of D8 connector, so like I said both in (D8 + and ground) and out (D8 + and - connectors) should always be 12 volts.

I don't know the value of the signal to the mosfet (I can try with my board and see if it matches your 1 volt, if so the definitely your mosfet is damaged.

Supply is not coming in d8 n the heat bed now getting heat up....
Plz help me ..