Control of Gilson Minipulse 3 pump with Arduino

This pump has a run/stop switch pins that can be controlled by the dipital output of Arduino. The switch gets closed (RUN) when the digital value of the port is LOW. This means than when the Arduino is disconnected the switch is closed and the Pump runs.

How can I make the connections for the Pump not running when Arduino is disconnected?

A pullup resistor?

I have this same pump at work so I know what you are talking about. Easy way is to use a relay, specifically a DPST relay, apply 12v to the common pin, connect the NC pin to the pump, the no can be left floating, connect the coil to the arduino (ideally via something to isolate the inputs on the arduino from the back emf). When arduino is connected and the coil is activated no 12v, pump runs. disconnect arduino the relay goes off and supplies 12v to the pump, pump turns off. Additionally, if you dint activate the coil, the pump remains off.

Sorry for any typos or what not, sent using my phone.

PedroDaGr8: I have this same pump at work so I know what you are talking about. Easy way is to use a relay, specifically a DPST relay, apply 12v to the common pin, connect the NC pin to the pump, the no can be left floating, connect the coil to the arduino (ideally via something to isolate the inputs on the arduino from the back emf). When arduino is connected and the coil is activated no 12v, pump runs. disconnect arduino the relay goes off and supplies 12v to the pump, pump turns off. Additionally, if you dint activate the coil, the pump remains off.

Sorry for any typos or what not, sent using my phone.

ACtually, with the minipuls3, you just have to short the two pins on the motor start/stop to start the motor and open them to stop it. This is even easier because you can just use a simple NPN to short them. Remember to control the motor from the back, the pump has to be stopped via the front panel.

Thanks Pedro,

I am sure that with a NPN or a delay it will work, but following the instrument guide it should work with a TTL signal. Which is much more simple. In fact it works perfectly with the direct connexion to a digital Output of the Arduino, but the unique problem is that of been ON when port output is LOW, even when the Arduino is disconnected.

I am sorry but I do not know what is a Pullup Resistor.

giraflorens: Thanks Pedro,

I am sure that with a NPN or a delay it will work, but following the instrument guide it should work with a TTL signal. Which is much more simple. In fact it works perfectly with the direct connexion to a digital Output of the Arduino, but the unique problem is that of been ON when port output is LOW, even when the Arduino is disconnected.

I am sorry but I do not know what is a Pullup Resistor.

It does work with a TTL signal, just not the way you want it to. It is designed this way so that with nothing attached the front buttons control the device (having two sources of control could be a disaster in a work environment). So the problem is to get the device to behave how you want. Somehow you HAVE to apply >2V to that pin when the arduino disconnects. The easiest would be with a relay, like I said. There is no way around having to use extra hardware, unless you somehow dump the devices firmware and hexedit it and reflash the pump. 4

You could use a 4N32 optical isolator, a 5V supply, and a relay. Done, that should be all you need.