I am trying to open the latching Hunter Solenoid valves from a 3V Arduino. These valves require a 9V 10ms pulse. The current I think is well under 1A (no specs) since I am able to use a 9V battery + L9110S H-Bridge motor driver to open/close the valve with no problems.
I was looking into purchasing a 9V Step-Up Voltage Regulator from Pololu to help boost the voltage from one of the Arduino Output pins. This project will be running off of a 5V solar charger (5,000 mAH) plugged in via USB.
Here's the 9V voltage regulator:
My 3 questions:
How long would I need to OUTPUT power to the 9V regulator before it could produce enough voltage to open the valve?
Is the 9V regulator a good choice for sending pulses to open the latching solenoid? My assumption is that as long as the output pin to the regulator is LOW, the regulator will only be consuming 2mA (no-load quiescent current).
Is a 10K pull-down resistor needed at the OUTPUT pin to the voltage regulator?
Depends on the IC and caps on it. But most well under 1s
Don't know without specs of the solenoid. But with enough capacity you can probably always force it But 2mA quiescent current is pretty high. But if your supply can handle it then fine
Why would it?
Do you need the reverse polarity driving option of an H-bridge?
I do need the H-bridge. The latching solenoid is +/-9V.
I thought I might need the pull-down resistor to ensure when the Arduino is restarted it doesn't accidentally switch the regulator on, but I guess that's really only issue with switches.
I was looking into purchasing a 9V Step-Up Voltage Regulator from Pololu to help boost the voltage from one of the Arduino Output pins. This project will be running off of a 5V solar charger (5,000 mAH) plugged in via USB.
How long would I need to OUTPUT power to the 9V regulator before it could produce enough voltage to open the valve?
Is the 9V regulator a good choice for sending pulses to open the latching solenoid? My assumption is that as long as the output pin to the regulator is LOW, the regulator will only be consuming 2mA (no-load quiescent current).
Is a 10K pull-down resistor needed at the OUTPUT pin to the voltage regulator?
Thanks!
No you cannot boost the output of the 3V Arduino, you can use the Arduino output to switch the 9V output of the DC-DCconverter.
But not supply the power needed.
Arduino outputs are not suitable as sources of power as their output is rated at 40mA MAX(and what the other I/O is outputting)
What Arduino board are you using?
DC-DC converters do not grab energy out of the air.
If your DC-DC converter was to supply 9V at 10mA, that is 90mW of output power.
The input of the DC-DC converter would consume about 100mW of input power.
So if your input voltage is 3V, then the current required to power the DC-DC converter would be 100/3 = 33.3mA.
That doesn't account for any load surge that may occur when the DC-DC converter has power initially applied.
czu001:
3) I thought I might need the pull-down resistor to ensure when the Arduino is restarted it doesn't accidentally switch the regulator on, but I guess that's really only issue with switches.
No, because the switching is done with the H-bridge. The boost converter is just always on (if you have a converter with enable you can turn it off). The H-bridge might need a pull resistor on it's input.
I'm using the smallest Pololu 3 to 12 volt converter, and it's doing exactly what they said it would. My circuit uses 50ma from a 500mah LiPo, but it shuts off completely when I'm not using it. This device (a multipurpose random number generator) is 8 months old, and I haven't had any problems. And the battery hasn't run down yet either.
Right now I have a circuit that works, but I have two separate power sources. I use a 3.7V Lipo battery to power the Arduino, and I use a 9V battery connected to the H-Bridge that uses the Arduino to switch pins.
The reason I wanted to bring in a voltage booster was to use a single power source. I assumed it would be ok to switch power to the voltage booster, but it doesn't sound like that's a good idea. The latching solenoid would only need to opened a few times a day (so 6 10ms pulses at most - 3 watering cycles).
Perhaps filling up a capacitor and dumping it to the H-bridge is a better idea? My goal is to just build a prototype that gets some decent battery life (a year would be fantastic).
ESP32 is a bit different again And a ESP32 can be very power hungry!
[edit]Confused you with this topic which is quite similar.[/edit]
And you can power all from a single source. But you can NOT use a transformer on DC And even with different voltage levels, just keep GND common!
With a latching solenoid power consumption probably is less important. But I would
OR make life easy and grab a lower voltage solenoid.
OR grab a converter with a enable line and a low quiescent current in sleep (2mA is high). And add a proper capacitor on the output. Now if you want to activate the solenoid, you enable the converter, wait a bit for the cap to charge, pulse the H-bridge to latch the solenoid and disable the regulator again.
So, I did find a 9V boost converter that has an ENABLE pin, has low quiescent current (less than 1mA without using ENABLE), and is not too expensive ($12).
I would still like to introduce solar to this project which is another reason I only wanted 1 power supply. Based on the feedback, I could hook this boost converter up to 3V on the board and use the ENABLE pin to lower current draw. It does draw current on initial startup, but I plan on putting the Arduino in deep sleep often (I assume deep sleep will not affect the startup of the regulator, just power down other components).
I apologize for jumping around a bit, but I am really wanting to keep one power source on the board if possible. Do you think this setup will work?
In regards to capacitor, if I am using the voltage booster do I still need the capacitor? If so why?
I've also found the following boost converter which is a lot cheaper. I'm not worried about reverse voltage protection since it will have a motor controller on the output which already has a diode on it.
First seems better suited although you can probably get the second converter working as well. And yes, you would still need a cap. Solenoids tend to be draw current in quite high spikes. The cap will buffer for that spike. The second converter with 300mA seems a bit low power but then again, I have no specs of the solenoid.
But because you only need pulses you can make some sort of, what is known in model railroads, as CDU (capacitor Discharge Unit). Simply connect the output of the converter to a large cap (470uF+) via a resistor. Choice the resistor in a way the converter can handle it even when shorted. So for example here, 300mA @ 9V +. 9V / 300mA = 30Ω so I would pick a 39Ω to be sure.
Now you connect the H-bridge to the capacitor which can deliver much higher current although for shorter amounts of time. So you enable the converter, give the capacitor some time to charge, and you enable the H-bridge to send a pulse. The voltage will drop a lot but if you choice the cap large enough the solenoid is already latched. Turn off H-bridge and converter and done.
The Arduino uses little power in (deep) sleep. And the last converter looks to be a SC4503 which has a shutdown current of less than 1uA.
This can run of solar just fine. But you would need to pick the right battery and charger. An easy way for example would be to use NiMH batteries because they are so easy to charge and don't mind trickle charging. 2 NiMH can run a 8Mhz Pro Mini and 3 a 16Mhz.
Thank you for the great information! This forum is incredible. I'll have to post my final circuit I ended up buying a few different boost converters from pololu, and I'm going to try them out. I'm not too sure of the specs of the solenoid either since Hunter doesn't post it, but it's a Hunter Industries DC Latching Solenoid. There's no spec on the actual current. It just says 9V.
I purchased the 9V DC Latching Solenoid. Unfortunately, I can't find the a valve that comes with the DC Latching solenoid (the solenoid is sold separately). The only document I can find on their website is here:
I've called Hunter, and they can't provide me with their current/resistance specs. But I've seen others do it.
I ended up choosing a different motor driver though (just ordered it). The L9110S works well, but I am experiencing battery drain on the 9V battery. I think it's due to the LED that is always on when the H-Bridge is powered.
czu001:
I've called Hunter, and they can't provide me with their current/resistance specs.
Pretty sketchy... But okay, with the resistor filling a cap thing you can buffer quite a bit. You might need a high value cap and wait a bit before firing but can be done. Some model railroad solenoids have peaks of >2A...
czu001:
I think it's due to the LED that is always on when the H-Bridge is powered.
Nothing a soldering iron (or snips) can't solve You need to remove them from the Arduino (together with voltage regulators) as well if you want long battery life.
But 2mA quiescent current is pretty high. But if your supply can handle it then fine 
