What is the PT500's programmable CPU for?
The PT500 runs software customisable for the user; the A, B, C, D digital and E analog inputs take application-specific functions. The hardware is fixed.
On the PT500 there is a processor running software that can be customised for the user. Its practical meaning is this: the A, B, C, D digital inputs and the E analog input can be assigned to functions specific to the application, and the operating logic can be taken beyond that of a standard direction/speed driver. The speed is set with the HIZ pot and the ramp with the RMP pot.
The difference from a fixed function driver
On a fixed function driver the meaning of the inputs and the outputs is set at the factory: one input means forward, the other means reverse, and this cannot be changed. If your application does not fit that scheme, the solution is usually to add a relay, a timer relay or a small controller outside. On the PT500, because the software can be customised for the user, how the module will respond to the inputs can be defined according to the application, and this need for extra hardware inside the panel decreases.
The interface available
- 4 digital inputs: A, B, C, D.
- 1 analog input: E - customisable. An analog input can be interpreted as a potentiometer position, a sensor output or a reference voltage.
- Pots: A1 (clockwise AntiSwitch current limit), A2 (reverse direction AntiSwitch current limit), HIZ (motor speed setting), RMP (ramp).
Having a separate AntiSwitch pot for the two directions is useful on mechanisms that meet different resistance in each direction: a lid that seats on a seal as it closes and the same lid moving freely as it opens want different thresholds. If the threshold is set wrongly, the movement is cut before it reaches the limit.
When customisation is needed
| Requirement | Approach |
|---|---|
| Forward-reverse movement, adjustable speed and ramp | The standard configuration is enough |
| A priority or sequence rule between the inputs | A matter for customisation |
| Different behaviour on a particular combination of inputs | A matter for customisation |
| Application-specific interpretation of the analog E input | A matter for customisation |
In practice the distinction rests on this: if you can describe your requirement with the sentence "press this input and go in this direction", the standard configuration is enough. When conditions such as "first", "but" or "if this input is open" start to appear in the sentence, customisation is on the table. It is also possible to build these conditions outside with relays and timer relays; which of the two is cheaper follows from the space in the panel and from who is going to maintain it.
Limits
The hardware side is fixed and it sets the design limits: 12-24V DC, 30 A continuous, 40 A maximum (15 seconds), IP67 protection and an independent AntiSwitch limit for the two directions. The software does not enlarge these limits; programmability does not gain current capacity. Nor is IP67 protection a software feature, it depends on the cable glands being tightened correctly during installation. In the same way programmability does not mean a safety approval either: functions such as emergency stop and load holding are left not to software but to hardware that falls to the safe side of its own accord when the power is cut. On products for which custom software is written, take into account from the outset that the return conditions are different.
What to do
If you have a need for customisation, describe the input and output logic of the application in writing: which input will do what in which state, under what condition the movement will be cut, and in which state the system will wake up when the power goes and comes back. Before the discussion, prepare the diagram of the existing panel and the current of the motor to be driven measured under load as well; whatever happens on the software side, the hardware limit follows from those two pieces of information. With that preparation the discussion concludes in a single round.
The full topic: DC Motor Driver Selection Guide