Melzi on a budget?

I am in the process of building the "sturdy" version of the Mendel90, using MDF for the frame and 10mm smooth/8mm threaded rods - this will be my first RepRap, and my first hands-on experience with 3-d printing. I am on a VERY tight budget, so this is a "Johnny Cash" project - as in, "One Piece At A Time".

One of the things I need is a Melzi controller. In my communications with NopHead, he told me that his Melzi boards are made specifically for him and are exensive - not really an option for me. There seems to be a plethora of Chinese Melzi boards available on the web. Some are cheap pricewise, some not so cheap (prices can vary wildly even for the same board - one going for $40 on one website can go for twice that on another website, or even between EBay listings). I am trying to find the best compromise between price and quality: I don't have a lot to spend, but I don't want a brick on arrival that needs to be returned, modified, repaired, or reprogrammed with additional hardware outside of my laptop, either. I have heard that there was a batch of Geetech Melzis that had problems with having the wrong MOSFETs and resistors, and I have also heard of SainSmart boards having a problem with built-in programs that do nothing but an axis test over and over and over agian. Whatever I get needs to have the bootloader already in it, as I don't want to have to spend extra money on an ISP programmer. Also want screw terminals, which the Geetech boards seem to be lacking in (they're mostly Molex KK terminals, from the photos I have seen). ElecFreaks has a reasonably priced board out, but I have not found any reviews on it.

Has anybody had good luck with any of the inexpensive Chinese Melzi boards "out of the box"? If so, which one did you use and where did you get it?

Anybody? Nobody?

Any electronics works with any printer. Buying cheap means you don't want to support open source developers, so you're on your own.

Edited 1 time(s). Last edit at 09/19/2014 07:19AM by Traumflug.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

I think you've already nailed the analysis. Cheap chinese boards often have issues with substitution. FET's might not be beefy enough to drive a heated bed, chip might not have the bootloader burned on it. It will be a bit of a crap shoot whether the board you get will work first time or not. If you have good electronics troubleshooting skills and are familiar with burning the arduino bootloader and loading firmware you might find that the cost savings is worth it. If you want something that is tested, and supported, a local seller is more likely to be what you need.

Bryan

On the contrary Traumflug, I DO support open source developers. In fact, I have purchased a fair number of parts directly from Chris ("Nop Head"). But since between Obamacare insurance costs and child support I only get to keep maybe 30% of the money I earn, if I want a rep rap within the next 5 years or less I sometimes need to go with a cheaper alternative and tweak it until it (hopefully) works.

Edited 1 time(s). Last edit at 09/20/2014 09:36AM by Rich K..

Why not go for a ramps/arduino setup? I bought a set for about 42bux shipped. It had the stepper drivers, smart lcd with sd card reader and a mega as a package. Smoking deal that I took a chance on, the reasoning was simple as I was not sure I could pull off my oversize design under my budget and skill. I went with a self built and self tweaked design and having no experience I did not want to spend tons of money. So far the gamble has paid off. The quality of the parts delivered exceeds the price paid.

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Modicum V1 sold on e-bay user jaguarking11

I wanted to go with the Melzi because that is what Nophead recommended for the Mendel90 - IIRC from his blog, he started with RAMPS or something similar and switched to Melzi. One thing about the Melzi is it will handle more current for the heated bed, apparently. Also, the Melzi is an "all-in-one" package with no seperate stepper drivers and wiring it up is easier. I decided to go agead and try a Melzi from Elecfreaks. We'll see how it works...once it arrives.

EDIT: this from Nophead's blog:

Quote

I changed the default electronics from Sanguinololu to Melzi because it includes the SD card interface and fan drive on board and uses screw connectors rather than friction fit. These are the only connectors I have found to be reliable in the long term...

Edited 1 time(s). Last edit at 09/25/2014 05:09AM by Rich K..

Well, so far, so good. The board (Elecfreaks) had the typical Chinese error of using 100k rather than 4.7k resistors for the bed and hotend thermistor hookups, but replacements were cheap and, after a minor struggle due to the tiny size of the resistors, I got the temps reading properly. Once I figured out what to do I got the firmware updated to Nophead's fork as well. We'll see how well it works once the rest of the printer is together.

Edited 1 time(s). Last edit at 10/06/2014 09:00PM by Rich K..