Retinaengrave DIY questions

Electronics related to CNC

Retinaengrave DIY questions

Postby austint » Mon May 28, 2012 3:47 am

Hello,

I am building a laser engraver and need some help from those who have used the retinaengrave controller from FSE. My main question is with the hardware side of things. Has anybody found a good logic level translator to change the 3.3 cmos level to 5v TTL ? The Retina engrave will only supply 2mA so the translator will have to have a high input impedance. I am using DMM tech servos and a laser power supply that needs ttl levels. Any help would be great!

Thank You
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Re: Retinaengrave DIY questions

Postby canadianavenger » Mon May 28, 2012 3:54 am

You can easily make a board with 74hct245 buffers to do the translation.
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Re: Retinaengrave DIY questions

Postby austint » Mon May 28, 2012 4:23 am

Thank You , I am reading the Datasheet. This IC is a little different . Most translators have a high and low input voltage for the two levels
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Re: Retinaengrave DIY questions

Postby Greolt » Mon May 28, 2012 6:13 am

A purpose built Break Out Board like this should be perfect.

http://www.homanndesigns.com/store/inde ... ucts_id=59

- Inputs can be 3.3V, or 5V logic levels
- All inputs and outputs are buffered and capable of supplying 24mA


Greolt
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Re: Retinaengrave DIY questions

Postby austint » Mon May 28, 2012 2:15 pm

Thank you for your post. That would be an easy way if it works. I wish I could see the schematic to it. I read that the 3.3 volt outputs from the retina engrave will not even supply enough current to connect directly to a optical isolator. It seems like the best bet would be to use a mosfet since it is more of a voltage controlled device and has a high input impedance. I found this breakout board on Sparkfun that uses a mosfet and a couple of 10k ohm pull up resistors. http://www.sparkfun.com/products/8745

The circuit has a 3.3 volt power supply connected to the drain of the mosfet through a 10 k ohm resistor . The gate is connected to the other side of the resistor along with the 3.3 volt input signal. The source of the mosfet is pulled to a 5 volt power supply . When 3.3 volts are present on the input side (gate) the mosfet is below the threshhold and is turned off. The source side of the mosfet is pulled high by the 5 volt source. This takes care of the logic one( 3.3 volts in and 5volts out ) . When the drain is pulled low by 3.3 volt source (retinaengrave) , the mosfet is turned on and pulls down source side to zero volts . This would take care of the logic zero. My only question is what exactly is the output device of the retina engrave? Will it be ok pulling down 3.3 volts and 5 volts through the 10 k ohm resistors? This will all make more sense when you look at the schematic on sparkfun.
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Re: Retinaengrave DIY questions

Postby macona » Tue May 29, 2012 9:09 pm

It will work fine. The issue with the retina engrave is the same with some PCs where they only output 3.3v on the parallel port. Homann makes some good stuff. I have his products in almost all my CNC machines and he is very helpful in getting custom stuff working.

-Jerry
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Re: Retinaengrave DIY questions

Postby austint » Tue May 29, 2012 11:58 pm

Thank you Jerry for your post.
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Re: Retinaengrave DIY questions

Postby Greolt » Mon Aug 20, 2012 12:23 am

Greolt wrote:A purpose built Break Out Board like this should be perfect.

http://www.homanndesigns.com/store/inde ... ucts_id=59


I have since discovered that this info I gave is not correct.

The Homann Designs BoB is an excellent product that complies with the LPT standard. Nothing wrong with that.

However the RetinaEngrave USB controller is NOT LPT compliant. I thought it was. The info on their site suggests that it is.

However the controller uses pin 15 as an output, (PWM laser power control). By the LPT standard as used by Mach3, EMC2, etc. pin 15 is an input.

The BoB that I mentioned above complies with that LPT standard, so that means it will not hook up, pin for pin, with the RetinaEngrave controller.

This can be overcome with a modified connection between the controller and BoB.

Just be aware of that.

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