stepper cause damage to picaxe?
- Thread starter fred_b
- Start date
BeanieBots
Moderator
The diodes are to protect from excessive VOLTAGE caused by back emf.
The CURRENT which passes through the diode will be the same as the current which was flowing originally to cause the back emf.
When driven as a generator, the VOLTAGE generated will be the same as the voltage required to move at that speed. The induced current will be whatever that generated voltage would produce across that resistance of winding.
To get a more a precise answer, fill in the words with numbers specific to YOUR motor and speed.
In reality, unless you've used small signal diodes (eg 1N4148) then it is unlikely to exceed their current rating. (but not impossible)
The CURRENT which passes through the diode will be the same as the current which was flowing originally to cause the back emf.
When driven as a generator, the VOLTAGE generated will be the same as the voltage required to move at that speed. The induced current will be whatever that generated voltage would produce across that resistance of winding.
To get a more a precise answer, fill in the words with numbers specific to YOUR motor and speed.
In reality, unless you've used small signal diodes (eg 1N4148) then it is unlikely to exceed their current rating. (but not impossible)
BeanieBots
Moderator
Very valid point Hippy.
Reverse (negative) voltage is just as much an issue as excessive high voltage and is often over-looked even by "professionals" when applying input protection.
Reverse (negative) voltage is just as much an issue as excessive high voltage and is often over-looked even by "professionals" when applying input protection.
The datasheet for the driver chip:http://www.datasheetcatalog.org/datasheets/90/366828_DS.pdf
The motor I am using is a 12v stepper.
Is it correct that spinning the stepper manually at high speed will generate a relatively high current at 12v.
Worst case, would it simply overpower the diode and try to charge the battery?
The motor I am using is a 12v stepper.
Is it correct that spinning the stepper manually at high speed will generate a relatively high current at 12v.
Worst case, would it simply overpower the diode and try to charge the battery?
BeanieBots
Moderator
Hard to say with stepper motors. Generation is more complex than with a 'conventional' motor.
Generally speaking, if the clamp diode is fitted such that back emf is passed to the supply rail, then driving the motor will try to raise the power rail. If the power rail is a battery, then yes, it will try to charge the battery.
A lot depends on the internal workings of the driver chip.
Generally speaking, if the clamp diode is fitted such that back emf is passed to the supply rail, then driving the motor will try to raise the power rail. If the power rail is a battery, then yes, it will try to charge the battery.
A lot depends on the internal workings of the driver chip.