Voltage into the Acorn board

[Philtrueman]

I have an Acorn board. I am making good progress on the Boxford lathe conversion. Just one question i have a motor driver controller that will only accept +5V input into the puls+ and Dir+ I know that i can use the DB25 plug for +5V Is it possible to feed in +5V into H1 for the pulse & Dir headers and feed in +24V into H4 for the home switches circuits.Are they separate circuits? They look like they are joined on the wiring diagram. My home switches work on 10-30V.
I could put a 2 ohm resister in the +24V wires to bring the voltage down to +5V.

[martyscncgarage]

I have an Acorn board. I am making good progress on the Boxford lathe conversion. Just one question i have a motor driver controller that will only accept +5V input into the puls+ and Dir+ I know that i can use the DB25 plug for +5V Is it possible to feed in +5V into H1 for the pulse & Dir headers and feed in +24V into H4 for the home switches circuits.Are they separate circuits? They look like they are joined on the wiring diagram. My home switches work on 10-30V.
I could put a 2 ohm resister in the +24V wires to bring the voltage down to +5V.

DO NOT FEED +5VDC to the Acorn headers!

5VDC Logic drives should be connected to the DB25 using a simple inexpensive breakout board. Is there a reason you are choosing not to use it?
Did you put the Acorn where the DB25 is not accessible?

If you want to *try* your +5VDC logic drives on the header you must:
Use the Acorn power supply 5VDC supply
Connect the +5VDC to the drive's +Pul and +Dir terminals (Do not connect any +ENA at this time as most drives come with the drive programmed to be enabled on power up)
Connect the drive's -Pul to the Acorn STP header
Connect the drive's -Dir to the Acorn DIR header

Test ONE drive and ONE motor on the bench with Acorn. If successful, add the second motor/drive and test.

REMEMBER, on a lathe Axis 1 is Z, Axis 2 is X, this is not negotiable. Leave it that way. Software is hard programmed for lathe to be that configuration.
Good luck!
Marty

[Richards]

The H2 and H3 connectors are Open-Collector circuits. They can use voltages between +5VDC and +24VDC; however, the voltage is NOT connected to the connectors. The voltage passes through the device controlled by the H2-H3 Open-Collector circuits. I drawn a very simple schematic that shows how an Open-Collector circuit works. Note that I'm using +5VDC as the voltage source. The resistor and the optocoupler represent a stepper-driver input. In this case, the (+) side of the stepper driver input (step or direction) is connected to +5VDC. The (-) side of the stepper driver input (step or direction) is connected to the corresponding pin on the H2 or H3 header. When the Acorn turns ON the H2 or H3 signal (step/direction/enable), current flows from the voltage source (+5VDC), through the stepper driver's input, through the Open-Collector device inside the Acorn, and then to GND (inside the Acorn). That's all there is to a basic Open-Collector signal. Often a pull-up resistor or pull-down resistor is added to sharpen the corners of the signal.

I've used the H2-H3 headers with my DM542 stepper drivers. I've used +24VDC as the voltage source (and a 2K 2W resistor to limit the current through the DM542 stepper driver step/direction signals. I've used +5VDC as the voltage source (no additional resistor was required with the DM542 stepper driver). I've also used the Acorn's DB25 connector to drive the DM542 stepper driver's step/direction signals. Both methods worked. An oscilloscope's signals of the step signals on the DB25 connector are better than the oscilloscope's signals of the signals from the H2-H3 connectors; however, adding the proper pull-up resistor made the 'scope traces about equal.

As Marty suggested, if possible, use the DB25 connector with stepper drivers. You won't have to fuss and mess with circuit tuning. If your only choice is the H2-H3 connectors, use an oscilloscope to check the signal shape and then tune the signal with resistors if necessary.

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Open_Collector.png (9.05 KiB) Viewed 1229 times

[Philtrueman]

Thank you Marty and Mike for such detailed explanations of the solutions to the other ways of connecting the drivers. I have ordered a DB25 break out board which saves soldering the wires onto the connector. I have temporarily soldered the wires onto a connector and all is working well. I will make the permanent wiring next week when i have fitted the home switches over the weekend.

[slice]

The DB25 breakout board does take up a lot of room. I purchased a DB25 connector and used that instead. Less space and cleaner in my opinion.

[martyscncgarage]

Thank you Marty and Mike for such detailed explanations of the solutions to the other ways of connecting the drivers. I have ordered a DB25 break out board which saves soldering the wires onto the connector. I have temporarily soldered the wires onto a connector and all is working well. I will make the permanent wiring next week when i have fitted the home switches over the weekend.

Breakout is more convenient for those that have trouble with the solder cups and can't do a clean job.
If you can solder then by all means use the DB25 connector.
I use crimp pins and DB shells that accept them. But I have the crimp tool.

Marty