memetis valves are current controlled to ensure that the very thin shape memory alloy actuator does not overheat during operation. But don't worry! The control mechanism is as easy as installing a simple LED driver circuit.
This page will introduce you to the electronic control options that memetis offers for initial product testing and prepare you for integrating the electronic control in your device prototype after the first testing stage is complete.
memetis valves are current controlled to ensure that the very thin shape memory alloy actuator does not overheat during operation. But don't worry! The control mechanism is as easy as installing a simple LED driver circuit.
We have created two versions of electronic control units (ECUs) to meet your needs for initial testing. ECU-S1 enables very simple testing of valve and chip actuator functionality, while ECU-P2 is made for more advanced valve testing when automation or current optimization is desired.
The use of ECU-S1 is straight forward – the on/off button turns the current supply to your valve or chip actuator either on or off. In the case of the ECU-S1-nc for memetis normally closed (NC) valves, the valve is powered and opened with a 500 mA continuous constant current. This current enables the opening of memetis NC valves within the temperature range of -20 °C to 60 °C (see technical data sheet).
NB! There are several ECU-S1 versions corresponding to the different memetis products. Current requirements differ between the valves and the chip actuator types and thus it's important to use the right ECU-S1 version.
The programmable ECU-P2 offers you to test two memetis valves with different current profiles and current amperage to optimize electrical power use in your exact setup. This can be done by using the graphical user interface that can be downloaded on our website. It is also possible to automate valve control when programming it with Python.
This ECU can be used to control two normally-closed memetis valves simultaneously. Please note that the ECU-P2 is not suitable for chip actuators.
A common use example for ECU-P2 is to set a higher current for a short time period to open the valve and then switch to a lower hold current that keeps the valve in the open state (further explanations about peak and hold current setting in the sections below). This allows reducing the valve power consumption if the ambient temperature allows it*.
* The actuators inside the valves work based on a thermal principle and the actuators are heated to open the valves. In higher ambient temperatures less current is required. The higher ambient temperatures, however, can mean slower valve closing time.
The ECU-P2 graphical user interface is made to allow switching memetis valves from your computer screen, tablet or Raspberry Pi, as well as setting manual current profiles for valve control without having to write it in code.
You can find the download links for the interface here.
ECU-P Interface Installation Video Guide here explains all you need to know for the first test.
The Quick Start mode, see selected on the left side panel, allows you to turn NC valves on and off using the enable/disable buttons similarly as with the ECU-S1. In this mode the NC valves, for example, are opened and kept open with a 500 mA continuous constant current.
To select the right current for your memetis product in Quick Start mode, click on the white button "NC Valve ..." and choose the product that you need to power.
Note! There are two options for bistable valves. Please consult the data sheet of the valve that you have in order to select the right current. Too high current can destroy the valves by over-heating the actuators.
The Manual Control mode, see selected on the left side panel, is where the current profile can be chosen and the exact values** set. Each of the values is explained in the next section. A total of five types of current profiles can be selected by clicking on „Pre-defined profile“:
Pre-defined profile - same as the Quick Start mode
Continuous - a single continuous current powers the valve for as long as the output is enabled ("Enable" button for each channel). In this case, the current and slew rate can be set manually.
Pulse - current type specifically for bistable valve testing where a constant current for a set duration of time is supplied to switch between the bistable valve states.
Peak & Hold - a peak current for a set duration of time is followed by a hold current that is kept until the valve is turned off. In this setting, both the peak and hold current can be set, plus the duration of the peak current.
Peak & Timeout - similarly as in Peak & Hold, both the peak and hold current strengths can be set, as well as the duration of each.
** Please check the recommended start values for testing on the specific valve data sheets.
Too high current can destroy the valves by over-heating the actuators.
If you have further questions, don't hesitate to reach out to support@memetis.com!
Depending on the selected current profile type, only the relevant values will be available for changing. The others will be disabled (Windows) or not appear at all (Mac).
For example, the Peak & Timeout setting allows changing peak current and duration, hold current and duration, as well as slew rate, i.e. current rise and fall time, see blue explanations on the image to the left. The other information that appears when controlling valves via the ECU-P2 graphical interface is explained in grey.
NB! If the ECU-P2 is shut off, the values won't be stored. The next time you want to use the interface you will need to change the default values again.
memetis ECU-P Interface allows controlling additional fluidic components that have compatible drivers. For example, all fluid system components in our valve test kits - Lee and Bartels pumps, Sensirion flow sensors - can be easily controlled within the graphical interface.
Programming the ECU-P2 with Python enables you to automate the valve control. The library that we offer lets you perform the same functions as using the graphical interface in the manual mode.
First, follow this guide to install the library and make sure the communication with your ECU-P2 works.
There are multiple ways how to implement the electronic control/connection in your setup. Below we offer some options to begin with!
The NC valve pins are 3 mm high, 0.4 ± 0.05 mm in width and have a 2.54 mm distance between the two pins. You can find the pin type data sheet here or see the part that we use here; part number 855-M50-3530342 with the middle pin removed.
Based on this information, you can design your own cables or solder your PCB on top of the valve pins.
memetis offers an embedded ECU that allows controlling one valve and is meant to be soldered directly onto your PCB. It has a small footprint of 17 mm x 19 mm and offers I2C communication that works with your microcontroller or Raspberry Pi. You can see the technical drawings here.
If you have more than one or few valves in your setup, you can create a spring contact connection to your electronics. We have technical drawings here for this solution as initial inputs to your design.
Here you can find three example circuit schematics to build a constant current source to drive a memetis valve on your own PCB:
If you are in doubt about the eletronic control aspects, please reach out to us via contact@memetis.com!
We also offer custom electronic development that fit perfectly into your setup. Our custom electronics can enable control of your whole fluidic system including pumps, sensors and other fluidic parts, as well as we can implement alternative connections on the valves directly. Don't hesitate to send us an inquiry.