Hi, this is my first post in the forum, ans hopefully I will do fine.
Here is my help request. I am looking to automate the cup filling system of a dental chair.
The system is fairly simple, the chair has a remote panel with several pushbuttons that activate different functions, and in particular the water solenoid valve to fill the plastic cups used by patients.
So far what I have found is that there is a control board, and the pushbutton activates an internal relay or transistor to operate the solenoid.
The pushbutton panel is very simple, as it has tactile switches that push the signal high (common is 5VDC). There is one common cable with 5V, and then a single return cable to the control board for each button.
What I have done:
I have successfully programmed an ATtiny85 controller in a test board to do what I want:
- A short button press (<1 sec) triggers the filling action for pre programmed time.
- During the filling process, a second press cancels the action (in case the cup was halfway full, to prevent overfill).
- If the button is pressed >1 sec, the controller activates the valve and enters programmed mode. It will record how long the button is pressed, and store that value in memory/eeprom (for persistent programming)
I have also taken several measures in the remote panel, as mentioned, the signal seems to be 5VDC, and closing the circuit activates the valve.
The panel is connected using a 14 pin connector (2x7 IDC type).
The activation using the ATTiny is via relay.
What I need:
I would like to interface the project with the control signal without doing any type of hardware hack to the pushbutton panel (I may isolate the pushbutton and connect it directly to my board, but that will void the warranty), so I am looking to interface my development using a pair of dupont cables/proper connector.
My issue at this time is that as there is a common signal cable (live with 5VDC) I cannot connect a common groud to detect the pushbutton press.
I see how I can activte the signal with my circuit relay, but am unsure how to detect the pushbutton press without trigering the valve.
Hopefully I have explained properly my idea.
Any ideas and suggestions will be very welcomed.
Regards