# so simple. . .but not at first glance

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#### TooHardForMe

##### New Member
Ok so, as the title says I'm at an impasse.
what I'm trying to do is find some kind of device that will extend and retract at about 1 second per extend/retract. I'm looking for a small device somewhat like an actuator but a little faster and can extend/retract automatically or autonomously until shutoff/turned on by a switch.
This device could be powered by anything from a DD battery up to a 12V power supply. If we could have a plug that connects to an outlet that would be convenient but not necessary.
I'm looking for specific names of parts or pre assembled devices that could meet the aforementioned plan or any other suggestions that might assist me in this rather tedious endeavor.

#### kubeek

##### Well-Known Member
What is the length of the extension? What force does it have to overcome? Does the motion have to be smooth, or any up down jerking motion will do?

#### Inquisitive

##### Super Moderator
Need more detail. What is the application.

#### TooHardForMe

##### New Member
Thanks for the responses!
kubeek - the extention can be anywhere between 1 inch and 5 inches, not a lot of force. Could be smooth or some jerking not too picky at the moment. About as much force as is needed to press a button. as for the force needed to press the button? umm not really sure :/

Inquisitive - the application is to literally extend out to press a button. . . .I was thinking to add a cushion or something on the button itself to absorb any excess force exerted onto the button so as to protect it from possibly being damaged by the actuator

*authors note*
I know it seems silly, but I am really just trying to find something to press a button. I will provide pictures as soon as time allows to better describe my dilemma.

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#### kubeek

##### Well-Known Member
Ok, the force required to push a typical button is quite a lot, I think somewhere in the order of 10N (about 2 pounds if you come from the 1800s). I asked about it because it seemed a solenoid might be a feasible solution. It might be, but only with 1" stroke, 5" would require a similarily huge solenoid.
An RC servo might work as well, but the force required could be pushing it a bit. Liner actuator seems a bit too slow or costly.
Do you have somthing in mind what will power this? Is it a stationary thing with mains supply or do you need to do it from batteries?

#### TooHardForMe

##### New Member
i was planning to make it stationary, as for power it depends of the device: if it has 2 wires for positive/negative then i'll tape a DD battery to the ends. If i can use a power outlet then it would be convienent.
my budget for this is around $500 #### Les Jones ##### Well-Known Member Most Helpful Member How about a small geared motor with a crank fitted on the shaft. If you want 3 inches travel then the crank pin would need to be 1.5 inches from the axis of the motor shaft. The crank pin would be connected with a link to rod that slides in a guide. There would be a hinged joint where the link connects to the sliding rod. It you chose a motor that rotated at 60 RPM (One rev per second.) then that would press the button every second. If the motor ran faster then you could arrange a micro switch that was actuated when the sliding rod was in the retracted position. the normally closed contacts on the micro switch would be connected in series with the motor. You would then have a relay with its contacts in parallel with the micro switch contacts that was pulsed every second by a NE555 timer for just long enough for the motor to move away from the retracted position. The micro switch contacts would then power the motor for the rest of the revolution. Why can't you just wire some relay contacts in parallel with the push button and pulse it with a NE555 timer (or similar) ? Edit. Sorry, I have just re read your first post and realise you want to use ready made items rather than bulding something. Les. #### kubeek ##### Well-Known Member Most Helpful Member Does it have to move, or is it just a simple stationary plunger? #### TooHardForMe ##### New Member I had thought of that kubeek, but I don't have access to soldering or wires . . .so its more convenient if the device is sort of pre assembled. in addition to this, I'm strapped for time. . . . If I could get someone to build this for me or find somewhere that it's pre built then I wouldn't have a problem forking the$ over for it. The piston or rod would have to move, yes
also I've thought to walk in a hobby store and explain to the clerk what I needed and what I was looking for but then there Isn't any store like that where I live. . . .so I thought to come online and get ideas

#### TooHardForMe

##### New Member
has to extend and retract as power is inputted to the device

#### Externet

##### Active Member
An electric extending/retracting antenna for automobile is not good ? Already built, 12V, off the shelf, cheap, widely available...

#### JonSea

##### Well-Known Member
Look at the automotive door lock actuator posted by Shortbus. it will push or pull with 3/4" of travel.

#### rfranzk

##### Member
Hello All,
I was thinking something like a door lock actuator which is actually a rack and pinion arrangement. A quick search on dc rack and pinion actuator showed this https://www.e-motioninc.com/Single_Rack_Actuator_p/p-358.htm It has quick travel and fairly high force. There are options for mounting brackets and power supplies also. The next challenge would be limit switches. Maybe an optical sensor or hall sensor?

#### Les Jones

##### Well-Known Member
I agree with Shortbus and Jonsea. You would just need to drive it with a DPDT relay such as this one connected to a 555 timer such as this one.
You would need to make sure that the door actuator had limit switches built into it. If it did not you would need to add them (Micro switches.) How long will the unit be opperating ? If it is 7 day 24 hour for years the actuator would probably not last very long. Giving some idea of your location (NOT your full address.) would be helpful in suggesting suppliers.

Les

#### Tony Stewart

##### Well-Known Member
This reminds me of how PC power Supply designs migrated over the years.

- 1st there was an AC Power switch on the front.
- then they had to isolate the switch from finger ESD getting into electronics so they used a long rod from front pushbutton to switch in rear.
- then they changed the design so it only switched a standby 5V to ground and the cable on MOBO to PSU carried this signal to turn on the power supplies
- now PC PSUs have the power switch in the rear or no switch altogether and just he IEC receptacle.

This makes me think the question is still at stage 2 when it could be done entirely different if he told us what is being switched.,

#### alec_t

##### Well-Known Member
Car windscreen wiper motor? It already has the reciprocating mechanism.

#### TooHardForMe

##### New Member
Les Jones - it would be operating between 4-5 hours at a time, those parts ideas are great only I wouldn't know how to build it. . . .and I don't have access to soldering or and tools to get the job done. so really it kind of has to be simply put together. . . .not sure if that helps or not

Tony Stewart - "if he told us what is being switched" thats over thinking it, this is way simpler than that

alec_t - I was hoping for something small, that could fit in your hand or slightly larger. that can rotate slowly and with force. enough force to press a button. Im at home right now and will add pictures as soon as I'm able to better describe my dilemma. I find it really simple but laughable that I can't find a small rotating device with force. . .

thanks for the responses everyone, once I post pictures of what I'm trying to do as well as a motivation for why I'm trying to do it will hopefully answer some questions. Les_Jones had suggested parts that I trust would get the job done, however I wouldn't know how to build it lol
another idea I had was to find a DC motor, easily power-able and spins! but those motors spin way to fast and when slowed down lose their torque.
Slider-crank mechanism, arrangement of mechanical parts designed to convert straight-line motion to rotary motion, as in a reciprocating piston engine, or to convert rotary motion to straight-line motion, as in a reciprocating piston pump.
https://media1.britannica.com/eb-media/90/4190-004-4DAAB8E9.jpg

hope this helps ~

#### shortbus=

##### Well-Known Member
Car windscreen wiper motor? It already has the reciprocating mechanism.
Not any of them I've worked on. They use a crank arm on the motor that turns with connectig links that go to the wiper arm "transmission"(the shaft that the wipers attach to) that has anothe short arm. It works like a crankshaft and pison in a motor. The motor it's self turns in a rotary motion, like most motors.