Linear Actuator (Motorised Lift for Sit/Stand Desk)

[nelsonic]

Raising/Lowering a Sit/Standing Desk manually is lame and means someone with reduced mobility (or strength) cannot operate it without assistance. (I have a relative with MS who would find it difficult to operate a "hand crank" for a manual standing desk)

A linear actuator can be used to lift the level of the desk to the perfect height.
See: https://www.youtube.com/watch?v=LVCE-rP9gnc
and: https://www.youtube.com/watch?v=ZiSZufAtpRE

The range of motion (which is referred to as the "stroke") for the IKEA Bekant motorised standing desk is 65cm - 125cm or 600mm of "Stroke".

see: #6

After doing a bit of research online, the cheapest 700mm linear actuator I could find was £95 including the mains transformer and command (£80 + £15 of shipping):
http://www.ebay.co.uk/itm/700mm-stroke-linear-actuator-with-manual-control-box-/181422094476

Spec:

The interesting bits are:

• 40mm/sec speed
• 700mm stroke (means we can exceed the range defined by IKEA i.e cater to taller people)

Strangely the Same eBay seller is charing £109 (for the identical product!) on their website:

http://www.popuptvs.net/product/standard-700mm-actuator-complete-with-hand-held-manual-control/

[nelsonic]

There was a cheaper unit with only 600mm of Stroke:

But it was shipped from China and the delivery estimate was too uncertain and most importantly the schematics (technical diagrams) were insufficient.

[nelsonic]

I searched Ali Express: https://www.aliexpress.com/w/wholesale-600mm-linear-actuator.html
e.g:

but could not find one that included the control unit and remote ...
So If the first design is a success we can investigate a cheaper unit in order to "mass produce". 👍

[nelsonic]

Did a bit of googling and found this data for the height of tables for children:

http://www.tarmakkids.com.au/table-chair-height-chart.php

[nelsonic]

Why is RS So expensive? http://uk.rs-online.com/web/p/products/7643455/

Granted this is a 8KN actuator (i.e it can lift/pull ~800kg) but still...!

[nelsonic]

Just saw this:

New Seller is offering TWO 600mm linear actuators for £31.52 inc shipping ...
http://www.ebay.co.uk/itm/24v-linear-actuator-motor-with-600mm-long-stroke-1000N-100kgs-load-/292060745090

How...?

Tried to purchase and saw:

Sent seller a message and watched the item. let's see if they reply.

[nelsonic]

https://youtu.be/RHZ7GaM0qvk

https://youtu.be/iQKGVWhH_EU

https://brentonc.com/2016/07/01/standing-desk-wiring-6-relays-to-2-gpio-pins
https://github.com/brentonc/RobotDesk

[nelsonic]

Good Beginner Explanation of how Linear Actuators work:

https://youtu.be/hpZl77cYBxo

Obviously ours is going to be controlled by a Pi or Pi-Zero rather than a rocker-switch,
but you get the basic idea.

[nelsonic]

https://www.aliexpress.com/item/Waterproof-12-24V-DC-Electric-Linear-Actuator-600mm-24in-Travel-3500N-770LBS-Black-Heavy-Duty-Linear/32843015584.html

Total: £355.88
Unit Price: 59.31 (£355.88 / 6)

The reason I like these is because they are super strong. 3500N = 356kg
So they can be used for other applications ...

[nelsonic]

https://www.aliexpress.com/item/700mm-Multi-function-Linear-Actuator-Motor-DC-12V-3500N-770LBS-350KGS-Heavy-Duty-Lift-mini-electric/32794829865.html

There isn't an incentive to buy now given that there will be a 10% discount in 7 days time! 🙄

[nelsonic]

Think I'm going to order these: https://www.aliexpress.com/item/Electric-Linear-Actuator-12V-24V-DC-Motor-600mm-Stroke-Linear-Motion-Controller-100-200-300-500/32825310053.html

Because they have a good Force to Speed ratio. 80KG @ 18mm/sec
If we use two per desk then an overweight person can sit on it without it breaking.
£48.78 per actuator including shipping. is good.
This will mean our material cost to make each desk will be around £170 (including wood & electronics).

Given that the 15% Sale "sale starts in: 7 days" ... I'm going to return to this next week! ⏳

[nelsonic]

These are 1000N (100kg) 800mm and cost $64.80 each (including "free" shipping)
https://www.aliexpress.com/item/32966503796.html

The only negative review is from a chap in the Czech Republic who complained that he had to pay import duties when they arrived ... 🙄

[nelsonic]

https://www.aliexpress.com/w/wholesale-1000mm-linear-actuator.html

[nelsonic]

Insightful video explaining the differences between linear actuators and servos.

https://youtu.be/L5tx64G1ilQ

I don't think need the level of control described in this video because I can derive the position in code.
So I think I'm sticking with "basic" linear actuators and will do anything fancy in software. 👨‍💻

[nelsonic]

Ordered the linear actuators for both the prototype sit/stand desk and bed from AliExpress:

The actuators are 12v DC.
That means I need a step-down power supply in order to use them on the 230 V mains electricity.

Sadly, the listing for the actuators does not specify how many amps.

But we can easily calculate it:
https://www.rapidtables.com/calc/electric/Watt_to_Amp_Calculator.html

Ordered 6 as I have 6 linear actuators on the way. (2 for my prototype desk and 4 for the bed

[nelsonic]

"Confirmation Timeout" ? 😕

Tracking information is temporarily unavailable

Sent a message to seller:

null null is here to help you.

🤦‍♂

@iteles could you please check the card that we used to place the order to see if the payment was taken?

[nelsonic]

null null is here to help you.

Very reassuring ...

[nelsonic]

Pickup tomorrow: https://msg.aliexpress.com

[nelsonic]

[nelsonic]

The 600mm linear actuators arrived yesterday! 🎉 😮
Which means I can start building my electronics! 🤯

[DanielJackson-Oslo]

@nelsonic

I'm going down the same path now!

What did you end up learning? Did it work?

[nelsonic]

Hi @DanielJackson-Oslo 👋
Stoked you found this thread. 😄

The linear actuators we got from China work well. No complaints. 👍
I'm definitely spoiled in that I have two desks one sitting and one standing.
I find that I seldom lower the standing desk, rather, I just unplug my laptop and switch when my legs are tired. 🧑‍💻

Are you thinking of building a standing desk from scratch or adapting an existing desk? 💭

[DanielJackson-Oslo]

Fantastic that they work well!

How stable are they? Could you, if you had four of them and fasten them properly, use them as legs?

I'm thinking of building from scratch, but it might be too ambitious.

[nelsonic]

The linear actuators are strong and stable. Really cannot fault them. ✅
Having four of them, one in each corner will work fine if you're going for ultra-sturdy. 4️⃣
Not many standing desks use 4 of them as I'm sure you discovered from your research. 🔍
What materials are you thinking of using for the frame; wood? steel?

[stefan-ml]

Hello,
Is desk useful?
Can you share parts of the desk? Which actuator you bought on AliExpress? I have plans to make a steel desk, and I need some true information.
Or post some pictures of your desk.
Thanks.