Problems trying to control 12V 3A Solenoid using boost regulator and 3.7V 18650 battery

Thread Starter

picotrain

Joined Apr 12, 2013
32
Hi,
We are working on a project where we want to control a solenoid valve rated 12V@3A https://www.adafruit.com/product/996

When we connect the solenoid valve across 12V from a DC power supply it works as expected and we measure about 0.6A through the solenoid valve coil.

We then wanted to control the solenoid valve using a 18650 3.7V LiPo battery source, so we obtained a boost regulator capable of delivering 4A and set the output voltage to 12V. Here is the boost regulator https://www.addicore.com/XL6009E1-Boost-Converter-p/ad456.htm

However the solenoid valve never actuates when being powered by the boost converter. We tried powering the boost regulator from a DC power supply just to rule out the battery with no change to the result.

We also had lying around a different boost regulator https://www.amazon.com/SMAKN®-Water...=2025&creative=165953&creativeASIN=B017CNAL56
capable of delivering 5A. When we power this boost regulator, its output switches the solenoid valve, however its minimum input voltage is 8V so we can't power it using a 3.7V source.

Can anyone suggest why our 4A boost converter wont drive the solenoid even though according to its rating it seems it should?
 

crutschow

Joined Mar 14, 2008
26,436
When we connect the solenoid valve across 12V from a DC power supply it works as expected and we measure about 0.6A through the solenoid valve coil.
I don't understand if it's rated for 3A, why you only measure 0.6A.
Something is wrong either with the spec or with your measurement.
 

Reloadron

Joined Jan 15, 2015
5,791
My best guess would be adjust the boost converter for a 12 volt output. Monitor the output and place you solenoid coil on it as a load while monitoring the voltage. Also as crutschow mentions above a 12 volt 3 amp solenoid coil would ab a 36 watt coil so I don'y get the 0.6 amp draw?

Most similar solenoids I have seen are generally about 8.0 watts. That would be closer and inline with the current you are seeing.

Ron
 

ebp

Joined Feb 8, 2018
2,332
I'm with crutschow - the numbers don't add up. All the values at the vendor site say the coil has a resistance of 4 ohms, so at 12 volts the current should be 3 A and the power should be 36 W - which is a lot! The fact it will operate with zero input pressure means it is direct acting (not "piloted"). A fairly high current would be expected for an orifice not limiting for 1/2" pipe. If your minimum pressure is greater than zero, a piloted valve will save a lot of power.

Realistically, the boost converter would have input current of at least 10 amps to drive the solenoid if it really requires 3 amperes. The boost converter has a peak switch current of 4 A, so there isn't the slightest chance it can run the valve, even if the cell could deliver 10 A. In fact it can't even deliver 4 A of output. The 4 ampere limit is the peak in the switch which will be higher than the average input current, probably by at least 20%. If the average input current were 3.5 A at 3.8 V, the output current at 12 V would be about 1.11 A at 100% efficiency. Less than 1 A is likely. The cell voltage probably is going to be even lower at that current level, meaning the output current is further reduced.

A boost converter that does not have adequate power at the input to deliver regulated output voltage will "instantly" go to maximum duty cycle, which will "flatten" the input supply - drawing as much current as it can, limited only by any circuitry designed specifically to set a limit - in this case 4 A.
 

ebp

Joined Feb 8, 2018
2,332
I found specs for an apparently similar valve saying 1.5 A at 12 V, but the (again, apparently same) valve at the site with a 24 V coil says 1.25 A, so my bafflement only grows.

Can you measure the coil resistance reasonably accurately?
 

Thread Starter

picotrain

Joined Apr 12, 2013
32
I found specs for an apparently similar valve saying 1.5 A at 12 V, but the (again, apparently same) valve at the site with a 24 V coil says 1.25 A, so my bafflement only grows.

Can you measure the coil resistance reasonably accurately?
The coil is 4.7 ohms.
I put 12V across it and measured 2.6A. Then I put 6V across it and measured 1.3A, so I know I can actuate it as low as 6V.
 
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