DB25 connector, and Pull up resistors

[midy]

So i've not started my wiring yet but one thing i keep seeing is it seems to be prefeable to use the db25 connector rather than the screw clamp connections on the acorn for step/dir. Is it better to use the DB connector or whats the differences

[DICKEYBIRD]

Preferable? I don't think so. Direct connection with 24v is better. I used the DB-25 connector so that the existing 5v homing opto-sensors on my lathe would work.

[cncman172]

You can actually use a hybrid approach. I used the DB-25 for STEP/DIRECTION since it is positive logic. The drive enables come from the screw terminals. If you have something like a Gecko G540 it is very clean to just plug in the DB25 cable between the two and your done.

Russ

[midy]

Thats the bit i don't understand - so the signals are different between screws and DB25? I assume one is positive and the other is negative logic? If so what does that mean? Also why use a breakout board when there is one on the acorn?

cheers

[diycncscott]

They are only are different in that the DB25 has an internal pull up resistor while the screw terminals do not. To make them behave exactly the same you could add 470 ohm pull up resistors to the Acorn step, direction and enable output.

Some drives have their own, internal pull resistors -which is why the Acorn screw terminal outputs do not have internal pull ups on the Acorn while the DB25 outputs do have a pull ups internal to the Acorn because the Gecko 540 and similar drives that connect via the DB25 do not have their own.

[DICKEYBIRD]

To make them behave exactly the same you could add 470 ohm pull up resistors to the Acorn step, direction and enable output.

Pardon my lack of electronics savvy but does this apply to sensor inputs as well? For example an opto-sensor used as a tool probe input? I have some of these sensors: https://www.ebay.com/itm/3Pcs-Opto-Opti ... SwG0BZcsWo that I plan to use.

If this is true, what is a good online supplier of said 470 ohm resistors that can be relied on to provide good quality & what wattage & tolerance should I specify?

[diycncscott]

Hi Dickey,

No, you don't need to do anything with the inputs.

For 5V use, "Any" 470 1/8 or 1/4 Watt resistor would be fine, they only pull about 10 ma and accuracy is not an issue since even a 10% swing is only 1ma.

For sourcing, I'd just go to Amazon and buy a jumbo variety pack like: Elegoo 17 Values 1% Resistor Kit Assortment, 0 Ohm-1M Ohm (Pack of 525)
it's like $10 delivered if you have prime. (they are 1/4 watt)

If your eyes are as old as mine, use a meter to check the values rather than try to see the color codes For 470's, I just look for yellow and purple And then just mark the tape to make it easier in the future.

[DICKEYBIRD]

Thanks a bunch Scott, the info on these simple little things is greatly appreciated!

[midy]

Thanks Scott. I will have to use a seperate 5Volt power supply as I have the leadshine type drivers. Does it have to be 1 amp as per the drawing, could it be more?

[DICKEYBIRD]

From my experience in such things, the drive will only draw as much current as it needs. A PS with more power/current availability will not hurt a thing as long as the voltage is correct. Now if you mistakenly build in a dead short somehow, the bigger the PS, the more magic smoke that is let out. Of course, I have no first hand experience in this.