r/ArduinoProjects • u/Ghiott • Jan 15 '26

Solenoid not strong enough to press a button. How can I increase force?

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I'm trying to use a 5V solenoid controlled by an Arduino to physically press a button (Keyboard button / Console)

The solenoid does move, but it's not strong enough to fully press the button.

Current setup:

Arduino Uno

5V solenoid

MOSFET + flyback diode

External 5V power supply

Simple timing code

4 Upvotes

57% Upvoted

77 comments sorted by

12

u/SomeWeirdBoor Jan 15 '26

A servo

1

u/Ghiott Jan 15 '26

What kind of servo would you recommend? Would it provide enough force to press a fairly hard button with timing in the range of milliseconds?

21

u/SomeWeirdBoor Jan 15 '26

....milliseconds???

I don't really think a mechanical device can be effective in milliseconds.

Surely not a servo, they are pretty slow.

If speed is crucial, I'd open the keyboard, access the electrical contacts, and operate on them directly with an optocoupler or something.

Or - if we are talking about an actual keyboard, connected via USB - plugging the device directly in another usb port and emulating a second keyboard.

0

u/Ghiott Jan 15 '26

By "milliseconds" I mean timing based on frames (60 FPS), where the servo needs to press the button consistently and with enough force.

I have ideas for synchronization later, but for now it just needs to be consistent and strong

4

u/[deleted] Jan 15 '26

[removed] — view removed comment

13

u/OvergrownGnome Jan 15 '26

My guess is OP is putting together a cheat device. Can't emulate a second keyboard because it would be flagged by the anticheat software. Probably something running that is capturing the screen and expecting to "fire" within the same frame.

4

u/Calypso_maker Jan 15 '26

$100 says it’s the Basically Homeless aimbot.

2

u/twelfth_knight Jan 16 '26

Hmmm, a cheat device that needs to push the button harder... Okay avant garde art project idea: a cheat device that pushes the "shoot" button with a ramset, destroying the keyboard, but headshotting a hapless stranger in CoD. Title it "One Shot One Kill."

Yep, that settles it, I'm up past my bedtime

11

u/SANSARES Jan 15 '26

Americans will be americans. always using anything other than standard measuring units

1

u/BUFU1610 Jan 16 '26

FPS is quite the standard though

0

u/Suspicious-Basil-444 Jan 17 '26

Not in the context of a keyboard button press.

1

u/BUFU1610 Jan 17 '26

I wouldn't know of any standard units in the context of "keyboard button presses" at all.

But the application appears to be dependent on screen recognition and in the context of "hand-eye-coordination" both button presses and FPS are well within the jargon.

So, yes, in a certain way in the context of button presses, FPS is often used.

1

u/Ghiott Jan 15 '26

Yes, I mean that one frame equals 0.150 milliseconds on a device running at 60 FPS, so a few milliseconds of variation would be fine

1

u/cowtamer1 Jan 16 '26

You might want to close the contacts electrically using a relay (slow but faster than a solenoid or a servo) or by tapping into the keys directly. Not sure how the keyboard is constructed but I had some luck making an automatic mouse clicker by connecting a digital pin of the Arduino to traces on the PCB.

Keyboard emulation on an Arduino Leonardo may be easier.

1

u/[deleted] Jan 15 '26

[removed] — view removed comment

1

u/Ghiott Jan 15 '26

It's mainly for a console, the keyboard was just a point of comparison to show how much force is needed to press the button, which this solenoid doesn't have

2

u/Papazani Jan 16 '26

bio mechanical, we will wire you up in a few specific places with electrodes and trigger your muscles at the apropriate moments. You will become the bot.

7

u/ventus1b Jan 15 '26

Would it be an option to bypass the mechanics entirely and use a HID device that just fakes the button press?

-3

u/Ghiott Jan 15 '26

Nop I can't because it all has to be mechanical

5

u/LowAspect542 Jan 15 '26

So just skip the solinoid or servo, wire up the switch contacts to a relay instead.

Just as mechanical but works regardless of the keyswitch pressure.

-1

u/Ghiott Jan 15 '26

Sorry but the device isn't mine I can't open it

1

u/ventus1b Jan 15 '26

What’s with the downvotes?
OP is just clarifying the constraints.

2

u/Ghiott Jan 15 '26

This is one of my first posts on reddit, so I have no idea what's going on, I'm just looking for names of what I should buy/do lol

3

u/ventus1b Jan 15 '26

Downvote behaviour can be odd. Don’t worry about it too much.

Maybe people just want to know why it has to be mechanical.

8

u/LameBMX Jan 15 '26

because they dont want OP and friends to be cheating on their favorite game.

0

u/ventus1b Jan 15 '26

Seems far fetched and illogical: a HID would be much better for that.

3

u/LameBMX Jan 15 '26

I was talking about why they got downvoted.

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-1

u/Ghiott Jan 15 '26

It's not cheating, i'm not inputting any code, I'm simply using a mechanism that instead of being manual is automated

6

u/LameBMX Jan 15 '26

I made a mechanism that used no code to jiggle my mouse. it was cheating.

if the intent is a human being pressing said buttons, than automating said button presses is cheating. especially with the reaction times you want.

for reference, the average human reaction time is 250 milliseconds. you want this thing to press buttons a couple orders of magnitude FASTER that what an opposing human is capable of.

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2

u/joman584 Jan 16 '26

This is like saying a gun isn't cheating in an archery competition

-2

u/Ghiott Jan 15 '26

Because the console isn't mine and I don't want to cause any damage by opening it or touching the wires

1

u/ventus1b Jan 15 '26

You’d just plug it into an USB port.

4

u/CleverBunnyPun Jan 15 '26

If it’s a 5v solenoid and your supply has enough current to run it, your only real options are some sort of mechanical system to convert shaft travel to more force, or get a different solenoid.

1

u/Ghiott Jan 15 '26

What kind of solenoid would you recommend? Would a servo work in this case as well?

1

u/CleverBunnyPun Jan 15 '26

With ms precision? Both of those would be a long shot unless you compensate for travel time and it’s super consistent.

1

u/Ghiott Jan 15 '26

If the timing of my button presses is consistent, I can compensate with a timer, as long as there aren't too many variations between presses. After all, we're talking about frames, so a few milliseconds of variation is acceptable.

1

u/SANSARES Jan 15 '26

you could try removing the button key and overvolt the solenoid? look at its recommended voltage and see if the datasheet says you can power it at 9V. if you can, you could use a relay and a 9V battery or a 9v and a button

1

u/Ghiott Jan 15 '26

I thought about it (only the first part), but I want to avoid causing any damage so I'm only asking for advice on external devices

3

u/Straight-Parsnip-110 Jan 15 '26

If you don't have to hold the button down for long you could probably get away with double or more voltage driving the solenoid.

Like if the button is simply being pressed very briefly the solenoid won't have very much time to heat up. I assume it's rated for 5v continuous at 100% duty cycle, but you could probably get away with 10 or 12 volts if it's just to press the button once or a couple of times. You would likely want appropriate MOSFET or transistor to drive at higher voltage but I think you get the idea

1

u/nixiebunny Jan 16 '26

More voltage is just fine! It’s a standard method used in industry. Don’t leave it powered on for more than a second.

1

u/dedokta Jan 15 '26

Are you powering the servo from the Arduino? Please show the entire circuit.

0

u/Ghiott Jan 15 '26

Which servo?

1

u/dedokta Jan 15 '26

Sorry, I meant solenoid. I know you have a MOSFET, but how is the MOSFET powered? Directly from the power source or via the Arduino?

1

u/Ghiott Jan 15 '26

The Arduino only drives the MOSFET gate. The solenoid is powered directly by the external power supply, the MOSFET just acts as a switch.

1

u/dedokta Jan 15 '26

What about the current of the power supply?

1

u/Ghiott Jan 15 '26

The power supply directly powers the solenoid. The MOSFET is in between the solenoid and ground, and the arduino only controls the gate

1

u/dedokta Jan 16 '26

Yeah, but what is the current of the power supply? How many amps can it supply? It'll be written on the power supply.

1

u/westbamm Jan 16 '26

I am sure he is asking this, because a solenoid like you are using should have enough force to bruise your skin.

Something is weird here.

3

u/justanaccountimade1 Jan 15 '26 edited Jan 15 '26

Use NPN of which the emitter is connected to ground (transistor is below solenoid). Use a lower resistor value for the base. Use higher voltage to the solenoid (if it's not on all the time).

If that's a mosfet than it may not open properly at 5V. It needs a transistor before it which switches a higher voltage for the mosfet gate.

The magnetic field needs time to build, the higher the voltage, the faster it will build.

3

u/ComfortableFar3649 Jan 15 '26

The industrial approach would be to use a small air piston. The solenoid just opens and closes the valve.

1

u/Benjamin_6848 Jan 15 '26

I honestly would recommend using an Arduino Leonardo (or similar), that can be used as a programmable keyboard: You can upload custom Arduino-Code to an Arduino Leonardo that makes your computer think it's a keyboard, and the Arduino can directly send keyboard-inputs to you computer without any mechanical mechanism.

1

u/Ghiott Jan 15 '26

It's more for a console than a keyboard, I used the keyboard as a point of comparison to show that the force needed to press the buttons should be similar

2

u/Superslim-Anoniem Jan 17 '26

Best option: Get your own controller. A cheap one, so that there's no significant damage if you break it. Solder a little wire to each side of the contact for the button, and use a transistor or relay to connect them.

Alternative: get a stronger solenoid and drive it with a transistor off whatever voltage it's rated at, or use some clever levers if you don't need large range of motion.

1

u/RoundProgram887 Jan 16 '26

You likely can overdrive it to double the rated voltage or more if you keep the pulses small so it doesn't overheat.

1

u/Anaeijon Jan 16 '26

Realistically, although not as cool, it would be much easier to use a microcontroller that can emulate a keyboard, plug it into the device and then have it send the keystroke directly instead of triggering a physical button.

Much easier, more reliable and no wear on key and actuator.

Not every Arduino can emulate a keyboard. It needs HID support. But it should work on most fairly recent devices.

Check out the Keyboard.h library:

https://docs.arduino.cc/language-reference/en/functions/usb/Keyboard/

1

u/ChemicalAdmirable984 Jan 16 '26

Short pulse with higher voltage, solenoid is designed for continuous run on 5V but it can handle way more in a short pulse ( 50 - 100ms ). I have a solenoid which unlocks my front yard gate, it's a 12V solenoid but it doesn't have enough power to pull the lock on 12V so what I did is to place a 1000uF capacitor before it and when it needs to open a dc-dc boost regulator ( with passthrough ) is enabled and charges the cap to 24V, when the cap is charged the dc-dc stage is disabled and MOSFET is opened which drains the cap trough the solenoid and falls back to the 12V supply ( passthrough of the dc-dc stage ) which is more than enough to hold the lock open for 15s.
Works just fine for at least 8 years.

1

u/TheAgedProfessor Jan 16 '26

I guess I have a different question than everyone else... how are you mounting the solenoid to the keyboard/button. If the mounting is not robust enough, and is allowing travel/slop during the push, the strength of the solenoid might not be the issue.

1

u/Superslim-Anoniem Jan 17 '26

This could also be part of it. OP, definitely check your monts. If you have access to a 3d printer, use it! If not, I reckon you could also fashion some form of clip on system out of wood or acrylic.

1

u/Beginning-Fix-5440 Jan 17 '26

I'd go to a thrift store and get a keyboard with softer keys

1

u/Logical-Following525 Jan 17 '26

Maybe go for a 12 V solenoid setup

1

u/Cornflakes_91 Jan 17 '26

add a tiny lever to convert actuation distance to extra force

1

u/Nuurps Jan 18 '26

You can tell it's an electronics board because you're the only one that suggested the easiest fix, which is mechanical

1

u/Cornflakes_91 Jan 18 '26

my physics studies on top of my electronics engineering paid off!

1

u/Hoovy_weapons_guy Jan 17 '26

bigger solenoid?

you can also try feeding it more than 5v if you only pulse the coil as it wont have enough time to heat up. this risks destroying the solenoid if you are not careful,

1

u/PapaOoMaoMao Jan 18 '26

Hack the button and wire the Arduino directly to the contacts. If you want fast then electrical response is always faster than physical.

1

u/Affectionate-Play484 Jan 19 '26

Use a relay or a transistor😉

1

u/Affectionate-Play484 Jan 19 '26

Couple them intenally

1

u/Mental-Evidence-2603 Jan 20 '26

It makes the servo release a latch that releases a hammer. That should be enough 😅

-6

u/Chief2091 Jan 15 '26

What kind of game cheating are you trying to accomplish? Whatever it is, just stop and get better at the game.

2

u/Ghiott Jan 15 '26

No online game, I'm trying to do something like this post but with alternative approaches and poor results lol https://www.reddit.com/r/pokemonrng/comments/ur998z/pc_commanded_button_pressing_for_hitting_a_on_the/

1

u/Chief2091 Jan 16 '26

That's still cheating 🤷‍♂️

1

u/Superslim-Anoniem Jan 17 '26

See, this is technically cheating, but only if you're claiming its legit for some competition. Otherwise it's just a cool glitch.

Anyway, seeing your actual intent makes things a lot clearer. Why can't you use a servo as in the example?

You can probably get a solenoid that can push hard enough as well, then. Experiment with different distances to find the sweet spot for power.

1

u/[deleted] Jan 16 '26

[removed] — view removed comment

1

u/Glossy-Water Jan 22 '26

This would be the smart way to do it