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I tried to build a circuit that would allow me to push a washing machine's start button remotely using a solenoid as an actuator.

The solenoid is wired to a 9v battery which also powers an ESP8266 through LM7805 voltage regulator.

Unfortunately, after soldering all the components, I discovered that the soleniod does not produce enough force to actually push the button.

The solenoid I used has the following parameters (sellers ebay page):

Rated Voltage & Current DC 6V 0.15A
Power   3.4W
Action Form Push Pull Type
Force   
Stroke: 2mm 35g/0.08lb
Stroke: 1mm 80g/0.18lb
Power On Type   Intermittent 25%
Max Power On Time   1 Second
Body Size   20 x 12 x 11mm/0.8" x 0.5" x 0.4"(L*W*H)
Cable Length    5cm/2"
Material    Metal, Electronic Parts
Weight  14g
Package Content 1 x DC Solenoid Electromagnet

schematic

simulate this circuit – Schematic created using CircuitLab

I don't want to desolder anything. The solenoid and battery are connected with plugs into the board so I can replace them easily.

My question is: having these constraints, is there anything I can do to increase the force of the push?

Maybe I can replace the solenoid with a different one? Or plug something else instead of it? Can plugging different power source help?

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  • \$\begingroup\$ Use a power source that can deliver more power than a 9V battery. 150 mA is actually quite a strain for that type of battery, which was designed for circuits that require 10-20 mA at most. \$\endgroup\$ – Dave Tweed Jun 19 '16 at 20:42
  • \$\begingroup\$ * I'ld suggest to measure the consumption that you currently have and you'll probably coerce Dave's comment. * I am surprised that the coil is rated 6VDC and 0.15A which is under 1W while it is supposed to consume almost 4W? * The 6V rated voltage may be compatible with the fact that the battery can't drive the load. * If you have a 9V adapter that can deliver 0.15A, you can check if the circuit works with a better power source (and measure the characteristics). \$\endgroup\$ – le_top Jun 19 '16 at 20:55
  • \$\begingroup\$ Use large capacitor such as 68000uF in parallel to the battery might give enough current strength to do the job. However yr transistor may need to upgraded to low on-resistance MOSFET. \$\endgroup\$ – soosai steven Jun 19 '16 at 20:57
  • \$\begingroup\$ @DaveTweed What will be the effect of these suggestions on the LM7805 that is connected to the same power source? \$\endgroup\$ – Artium Jun 20 '16 at 18:08
  • \$\begingroup\$ @soosaisteven What will be the effect of the suggestion on the LM7805 that is connected to the same power source? \$\endgroup\$ – Artium Jun 20 '16 at 18:09
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Use a lever.

Presumably the button has much less travel than the solenoid, so you can put the solenoid at the and of a long rod and multiply the force.

enter image description here

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    \$\begingroup\$ assuming he got the space to place that and that the solenoid push far enough. \$\endgroup\$ – MathieuL Jun 21 '16 at 14:35
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I experienced a similar issue with a different application.

In my case, I was controlling a solenoid with an N-Channel Mosfet. Like you, I used a current limiting resistor for the transistor's gate (base in your case). Its value was 260 ohm, which caused the source to gate voltage to be around 2V, too close to the threshold voltage. Lowering into it to 50 ohm increased this to 4V, allowing the transistor to be "more open or conductive" if you will, thus allowing the solenoid to draw more current from the battery.

It may work for you too, just be cautious not to exceed base max current. Good luck!

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