Wiring relay for Heatbed

hello all,

so ive been running my printer a lot and today my heat bed started cutting off at around 40C. i felt the fuse on the board and it was smokin hot. I have a wiring diagram for using a relay to wire the heatbed to the PSU instead of the ramps 1.4 board. Problem is I cant figure out how to wire the Relay I got. Im putting up a picture of the relay and diagram of whats on it. also will link the data sheet of relay, and wire diagram I plan to use. I know just enough to get myself hurt and would rather have another set of eyes look this over.
Thank you in advance.

Relay Data Sheet
[www.te.com]

Hi,
I would say that the relay you are using is not suitable for this application.

The correct one as shown in the wiring diagram should be a 12V 30A SPDT (single pole double throw) type Automotive relay
Ensure it's suitable to switched with a 5v Arduino signal something like this would be suitable
[www.dx.com]

It would also be a good idea to place a fuse in line with the positive power feed from the PSU rated about 15A.
An automotive blade type fuse will work and protect against any short circuits.

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Supporting 3D Printers with Parts and Build services.
Printer: Ormerod 2 (528.4) Duel extruder set-up with Aluminium X-Rib, RRPro Firmware v1.11-ch (2016-04-08)

this relay will work perfectly. Don't use a 5 volt one because you are going to connect the relay to the 12v heatbed output. of your ramps
using a fuse is a very good suggestion between the power supply and the relay, use high quality fuss box els it will also get very warm.
how many watts is your bed?

here is the datasheet
[www.mouser.com]

page 3 shows how to connect you have the '2 from A' version.

Edited 1 time(s). Last edit at 03/09/2016 05:59AM by amigob.

Quote
amigob
this relay will work perfectly. Don't use a 5 volt one because you are going to connect the relay to the 12v heatbed output. of your ramps
using a fuse is a very good suggestion between the power supply and the relay, use high quality fuss box els it will also get very warm.
how many watts is your bed?

here is the datasheet
[www.mouser.com]

page 3 shows how to connect you have the '2 from A' version.

Wasn't suggesting using a 5v relay; The relay that I linked to will take a max input voltage of 30v DC with a 30 amp load, that's plenty to power a heated bed.
A relay uses a small voltage and current to switch a larger voltage & current.
The heat bed output pin from the ramps board will be 5v with a small current and the heated bed will be attached to the load side of the relay, with one wire at 12v and the other at 0 v (ground). The most common and IMHO the best relay to use is an automotive relay which won't pull than 1/4 of an amp from the ramps board. Check the resistance value for the coil side of the relay and use Ohm's law to workout out the current flowing.
When electronics run warm it's because that are being over worked

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Supporting 3D Printers with Parts and Build services.
Printer: Ormerod 2 (528.4) Duel extruder set-up with Aluminium X-Rib, RRPro Firmware v1.11-ch (2016-04-08)

> The heat bed output pin from the ramps board will be 5v with a small current and the heated bed will be attached to the load side of the relay,
You do it again :-)
Where do you think that you will find the 5v on the ramps board ? It is 12V, how do you think that people attach the headbed directly to the ramps ?

0.25 A for the relay is peanuts for the heatbed connection also for the ramps , it was designed for the full current ( if you have a good ramps ) but even the very bad ones can easily handle 0.25A

If he has that relay use it. but don't expect that you can do PID with it.

Quote
amigob
> The heat bed output pin from the ramps board will be 5v with a small current and the heated bed will be attached to the load side of the relay,
You do it again :-)
Where do you think that you will find the 5v on the ramps board ? It is 12V, how do you think that people attach the headbed directly to the ramps ?

0.25 A for the relay is peanuts for the heatbed connection also for the ramps , it was designed for the full current ( if you have a good ramps ) but even the very bad ones can easily handle 0.25A

If he has that relay use it. but don't expect that you can do PID with it.

Upon the ramps board the connection for the heat bed will be on the load side of a 3 pin Mosfet (source & drain) and there will be 5v from the MCU to the gate pin.
The MCU will PWM the heat bed output pin connected to the gate pin of the mosfet thus controlling the heat bed.
I suggested that the relay that they have is incorrect and the diagram that they linked to shows a better one in the form of an automotive relay and connecting the coil side of the auto relay to the heated bed terminals upon the ramps board, that will operate the relay.

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Supporting 3D Printers with Parts and Build services.
Printer: Ormerod 2 (528.4) Duel extruder set-up with Aluminium X-Rib, RRPro Firmware v1.11-ch (2016-04-08)

Salve non so se sia la sezione giusta ma anche io ho un problema con il relè della mia seconda stampante, premetto che sulla prima stampante il relè funziona alla perfezzione mentre nella seconda stampante ho un problema che non riesco a capire, in pratica collegato il relè alla ramps da repetier accendendo il piatto si vede il led che si accende mentre se spengo il led si spegne dunque vuol dire che il relè funzione ma il problema è che il piatto rimane sempre acceso appena accendo l'alimentatore già comincia a scaldare ancora prima che io lo accenda da repetier vi posto il collegamento sia del relè e del letto riscaldato se poi qualcuno mi puo essere di aiuto...ha dimenticavo di dire che il termistore funziona e rileva la temperatura. (GRAZIE)

Edited 3 time(s). Last edit at 03/25/2016 07:00AM by Max-29.