Wiring a Solid State Relay to Ramps

I am thinking of replacing the relay on my Makerfarm i3v 10" with a solid state relay & adding one to my FolgerTech Delta, but wanted to know how to hook it up before ordering a couple. I found these 2 images. The 1st one I don't understand why having the heat bed + going to the SSR - would be a good idea. http://3dprintboard.com/showthread.p...large-heat-bed!!!
This 2nd one shows what makes more sense to me. http://www.soliforum.com/topic/9004/...-installation/
Do either of these look like the correct wiring? Think I also read on here that I need 12v wired to the 11amp connection on the ramps also.

Also does anyone have a recommendation of which relay to buy?

-David

Heat beds typically aren't really polarized, so any + and - reference doesn't matter. The only situation I am aware of where it does is if the heat bed is equipped with an LED to indicate when power is on.

With RAMPS, people normally wire the SSR control inputs to the D8 output that would otherwise power the heat bed. For the D8 output to work, you need 12V connected to the 11-amp power input.

I think most people get an SSR off Amazon. You can search the Makerfarm subforum for "solid state relay" for some threads that provide links. The general comment I'd have is that going higher in a current rating is better, since the higher current relays will typically also have a lower on-resistance. This maximizes the amount of power going to your heat bed and minimizes the power lost as heat in the SSR. You also want to make sure the SSR is for DC loads, not AC. Unlike mechanical relays, that makes a difference for SSRs.

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Originally Posted by printbus

Heat beds typically aren't really polarized, so any + and - reference doesn't matter. The only situation I am aware of where it does is if the heat bed is equipped with an LED to indicate when power is on.

With RAMPS, people normally wire the SSR control inputs to the D8 output that would otherwise power the heat bed. For the D8 output to work, you need 12V connected to the 11-amp power input.

I think most people get an SSR off Amazon. You can search the Makerfarm subforum for "solid state relay" for some threads that provide links. The general comment I'd have is that going higher in a current rating is better, since the higher current relays will typically also have a lower on-resistance. This maximizes the amount of power going to your heat bed and minimizes the power lost as heat in the SSR. You also want to make sure the SSR is for DC loads, not AC. Unlike mechanical relays, that makes a difference for SSRs.

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Thanks for the info printbus. I will do some research before deciding which one to buy.

Hi

The Amazon ones that come for < $20 with the heatsink seem to work fine. The one I have is a 100A version. It was still dirt cheap. The relay and heatsink never seem to get hot. You can drive them with just about any signal off of the Ramps. Configuration wise, it is *much* easier to just hook them to the same output as the "gizmo" normally uses. Marlin is configurable enough that there are a number of other options....

If you did go with a SSR you should really consider setting it up like an 8" heater hooked directly to the onboard FET with PID control. I changed over from a relay because with Bang-Bang I was get poor regulation of temp and on 0.1 mm layers there was enough glass warp to make the tip drag on occasion. Also with a translucent PLA I'd get slight changes in color on the first couple of layers as it heated and cooled leaving sort of diagonal stripes although they don't really show on the finished print. I did however visually illustrate the wide variance in temperature compared to PID control. It works a lot better now with the SSR and PID enabled and AutoPID run for the bed.

Thanks. I bought this one: https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1 , but not sure when or if I will hook it up. My printer is working well with no heat bed. I am using blue tape & glue stick for PLA & PETG. Small parts I do not use the glue stick. I am almost finished a 6 hour print of a vertex for an Emmett-Delta printer & the print looks really good. I just changed my wades extruder to a titan extruder last week.

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Originally Posted by PyramidDave

Thanks. I bought this one: https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1 , but not sure when or if I will hook it up. My printer is working well with no heat bed. I am using blue tape & glue stick for PLA & PETG. Small parts I do not use the glue stick. I am almost finished a 6 hour print of a vertex for an Emmett-Delta printer & the print looks really good. I just changed my wades extruder to a titan extruder last week.

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Hi

If you run the 40A relay on the heated bed, you probably should have a heatsink on it.

I have never used anything other than hairspray on glass with the Makerfarm printers. It has always worked great for everything I have printed. That includes PETG, PLA, ABS and a few odd filaments.

Bob

I should have mentioned I did order a heat sink also. That has not arrived yet.

I tried the hair spray & used that for the 1st year, but occasionally something would lift up on a corner. I do not print ABS though. The only problems I have with blue tape & glue is if the bed is not level or I did not adhere the tape down well.

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Originally Posted by PyramidDave

I should have mentioned I did order a heat sink also. That has not arrived yet.

I tried the hair spray & used that for the 1st year, but occasionally something would lift up on a corner. I do not print ABS though. The only problems I have with blue tape & glue is if the bed is not level or I did not adhere the tape down well.

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Hi

The only times I have had a lift with hair spray have been on non-level beds or on ABS. There, the print fractured about as often as the corner lifted. With the layers separating on 270C ABS, it's not an adhesion issue .....

Bob

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Originally Posted by PyramidDave

I should have mentioned I did order a heat sink also. That has not arrived yet.

I tried the hair spray & used that for the 1st year, but occasionally something would lift up on a corner. I do not print ABS though. The only problems I have with blue tape & glue is if the bed is not level or I did not adhere the tape down well.

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I have mine heatsinked but if you have a V-slot framed printer you could probably get away with attaching it to the aluminum frame and use that as your heatsink for up to 10" heatbed. A 12" would probably be pushing it and need a regular heatsink. I attached my heatsink to the v-slot (Pegasus 10, full metal) and found a printed cover for the SSR on Thingieverse and it actually looks pretty cool, almost a Steam Punk look with that heatsink

My first printer didn't have a heated bed so I used the painter's tape for about a year and a half but I prefer the heated bed once I started using one. I do occasionally use the blue tape for 'effect' when I want a matte rather than a shiny surface. I make a lot of electronics project enclosures and on many projects it just looks more professional. Large flat pieces I usually include a brim which helps considerably. Also the auto bed leveling helped getting an more consistent 1st layer height which seems to help noticeably with adhesion and warping.

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Originally Posted by printbus

. You also want to make sure the SSR is for DC loads, not AC. Unlike mechanical relays, that makes a difference for SSRs.

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AC SSRs use triacs and DC SSRs uses MOSFETs .... One advantage of the higher current rating SSRs is if you get one rated at 100A you can ditch the heatsink for a 15A-20A heater. Frankly once you approach 20A@ 12V DC it's time to raise the voltage to 24V or go to an AC heater. Things just get too lossy, connections more problematic, etc. It's a big part of the reason I went with a 10" rather than the 12". I have my doubts about the longevity of that 12" pcb heater at 12V. Look at all the trouble they go to for the 12V high amp connections on a desktop computer with 4 parallel 12V lines to the motherboard and 2 or more in parallel to a video card

Hi

The need for a heatsink varies a *lot* depending on which one you get. A 100A relay will heat up less at 20A than a 20A relay will. Since P = I^2 x R (most modern relays are resistive) the difference can be anywhere from 5X (straight voltage drop) to 25X (resistive). Indeed the 100A relay might dump more power at 100A than the 20A relay does, but it isn't more than 2X in most cases.(yes that messes up the numbers even more).

Bob