I only want forward-reverse direction control, no speed setting: which model suits me?
The ST42 suits direction and on/off control: it carries 4 A per channel and 8 A in total; if the current requirement is higher, the 15 A KS250 or the 30 A PT500 is the safer choice.
If you only want forward-reverse direction or on/off control, the ST42 suits exactly this purpose: it drives the motor from an RF remote control receiver, a manual button or a panel output signal. The board also has speed and ramp adjustment; you do not have to use it if you do not need it. Typical areas of use are automatic gates and barriers, mini cranes and lifting arrangements, DC linear actuators and in-panel automation. The only item that makes the decision difficult is current; do not choose a model without measuring the current the motor draws under load.
The decision is settled by current
The ST42 is rated for 4 A per channel and 8 A in total continuous. To see whether you stay under that limit, the right method is to run the motor with its real load and read the current with a clamp meter; measuring how many amps the motor draws is a job of a few minutes and settles the choice on its own. If the measured value is going to strain that limit, move to the models rated for a higher current:
- KS250: 12/24V, 15 A continuous, 45 A peak (5 s), IP45.
- PT500: 12-24V, 30 A continuous, 40 A maximum (15 s), IP67.
When you measure, note the steady running current and the peak at the moment of starting separately. The difference between continuous current and peak current is decisive here: the peak value is valid only within the time window stated, it is not a continuous running rating.
Which model for which requirement
| Control requirement | Measured continuous current | Suitable model |
|---|---|---|
| Direction / on-off only | Up to 4 A per channel | ST42 |
| Direction, automatic stop at the end of travel | Up to 15 A | KS250 |
| Direction, speed setting and outdoor use | Up to 30 A | PT500 |
Two things that pay off even if you do not want speed setting
The built-in AntiSwitch of the KS250 and the PT500 finds the end of travel by current sensing; that way you do not need to run external limit switches. On gate, barrier and actuator applications this does away with two switches, two cable runs and a calibration job. The second gain is the ramp: on a change of direction the motor does not jump from zero to full power, so both the mechanical strain and the starting surge fall. Even if you never use the speed setting, you can leave the pot fully open and benefit from these two functions.
Where this choice does not fit
- If two motors have to move independently: motors connected in parallel to a single driver turn in the same direction and at the same speed; separate control needs a separate driver.
- If you have to stop at an intermediate position: the current threshold only detects the end of travel. For a repeatable stop at a point in between, position feedback or an external switch is essential.
- If you are expecting a safety function: AntiSwitch and the current limit reduce mechanical strain, but they are not circuits designed for personnel safety. The emergency stop has to be separate and in hardware.
- If the board will sit outdoors: inside a panel and in the open are not the same; decide whether you need IP45 or IP67 according to the mounting location.
What to do
Run the motor with its real load, measure the continuous current and note the starting peak. If the value is below 4 A per channel and you only want direction control, the ST42 does the job. If the current is close to that limit, or if you want the end of travel detected automatically, choose the KS250 or the PT500; changing the module later means redoing the cabling, the mounting and the setting.
The full topic: DC Motor Driver Selection Guide