basic question about Driver input signals
- tommylight
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17 May 2021 00:29 #209189
by tommylight
Replied by tommylight on topic basic question about Driver input signals
They will work either way.
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- rodw
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17 May 2021 02:51 #209191
by rodw
No I've used these. That diagram is for a BOB for Mach3 which is active low. The straight through connection is all you need to the +step and -step outputs to the Mesa Stepgen pins. The resistor shown is used only if you are running a stepgen with > 5 volts.
Replied by rodw on topic basic question about Driver input signals
Neither driver has differential inputs (DM860A nor DM542T). Both drivers have ordinary inputs with an optocouplers. See picture.
cdn.goodao.net/longs-motor/7af08ace2.jpg
A better option is to connect only DIR +, STEP + and GND signals (or DIR-, STEP- and + 5V).
No I've used these. That diagram is for a BOB for Mach3 which is active low. The straight through connection is all you need to the +step and -step outputs to the Mesa Stepgen pins. The resistor shown is used only if you are running a stepgen with > 5 volts.
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- andypugh
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17 May 2021 12:41 #209224
by andypugh
Both ends of the optocoupler are broken out to the terminal block, which means that they will work with differential wiring as long as the optocoupler maximum reverse voltage > 5V.
I suppose there is no real way to know what the max reverse voltage of the optos is, but one of the datasheets for the DM860 says:
"4. Control Signal Connector (P1) Interface
The DM860 can accept differential and single-ended inputs (including open-collector and PNP output). The DM860
has 3 optically isolated logic inputs which are located on connector P1 to accept line driver control signals. These
inputs are isolated to minimize or eliminate electrical noises coupled onto the drive control signals. Recommend use
line driver control signals to increase noise immunity of the driver in interference environments. In the following
figures, connections to open-collector and PNP signals are illustrated. "
So they illustrate PNP and NPN connections (Or Ying and Yang) but recommend line-driver (ie differential)
Replied by andypugh on topic basic question about Driver input signals
Neither driver has differential inputs (DM860A nor DM542T). Both drivers have ordinary inputs with an optocouplers.
Both ends of the optocoupler are broken out to the terminal block, which means that they will work with differential wiring as long as the optocoupler maximum reverse voltage > 5V.
I suppose there is no real way to know what the max reverse voltage of the optos is, but one of the datasheets for the DM860 says:
"4. Control Signal Connector (P1) Interface
The DM860 can accept differential and single-ended inputs (including open-collector and PNP output). The DM860
has 3 optically isolated logic inputs which are located on connector P1 to accept line driver control signals. These
inputs are isolated to minimize or eliminate electrical noises coupled onto the drive control signals. Recommend use
line driver control signals to increase noise immunity of the driver in interference environments. In the following
figures, connections to open-collector and PNP signals are illustrated. "
So they illustrate PNP and NPN connections (Or Ying and Yang) but recommend line-driver (ie differential)
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- rollfree
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17 May 2021 23:45 - 18 May 2021 00:07 #209292
by rollfree
Replied by rollfree on topic basic question about Driver input signals
Yes, it will also work in STEP + and STEP- wiring. I wrote that single ended wiring is better, not that it's the only option.
Differential connection makes sense when the driver has a differential receiver at the input. It is contained rarely in stepper motor drivers, but it is included in a lot of servos. Typically, the 26LS32 or 26C32 circuit is used.
Using differential excitation of a driver that has a common optocoupler at the input does not bring any advantage. On the other hand, it has the disadvantage that you either unnecessarily burn energy on the resistor and anti-parallel diode most of the time (if the driver has this protection diode), or you strain the optocoupler LED with reversal polarity.
Differential connection makes sense when the driver has a differential receiver at the input. It is contained rarely in stepper motor drivers, but it is included in a lot of servos. Typically, the 26LS32 or 26C32 circuit is used.
Using differential excitation of a driver that has a common optocoupler at the input does not bring any advantage. On the other hand, it has the disadvantage that you either unnecessarily burn energy on the resistor and anti-parallel diode most of the time (if the driver has this protection diode), or you strain the optocoupler LED with reversal polarity.
Last edit: 18 May 2021 00:07 by rollfree.
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