Schematic for my useless box (first project)


For my first project, I want to build a useless box. After reading several discussions about servos, regulators and capacitors, I drew my electrical schematic.
The power supply will be 6 AA batteries.
To power the servos it will go through a regulator.

Can you tell me if my schematic looks correct to you?

thanks in advance.

(sorry if I make mistakes in english)


Please can you read How to get the best out of this forum

Please don't use links to external sites like that, please post your schematic on this web site, not elsewhere. You will have to create an image of the schematic, for example a jpg file and upload that.

You are more likely to get help if everything someone needs to help you is here rather than elsewhere on another site.


I had tried to put the document directly in the forum but I had a message which told me that I was too young on the forum to put attachments. now I can, I correct my post.


1 Like

No. So many things wrong!

You do not use regulators on battery projects. You might use switchmode "buck" converters if there is a real need to do so, but certainly not series regulators.

The servos run from 5 or 6 V. That is four alkaline "AA" batteries. Arguably, if you use four NiMH batteries, you can use that for the servos, and also power the Nano.

You do not need to connect the switch to both 5 V and ground. You connect it to ground, and use INPUT_PULLUP mode on that Nano pin. In most cases, the 10k resistor is quite unnecessary.

The big (well, second biggest after that) design problem is that the "Useless Box" needs to be permanently powered, but draw no power until activated. So you cannot leave the Nano powered and you certainly cannot leave the servos powered as they draw resting current.

I haven't built a "Useless Box" myself, so I am not sure how this is usually managed in the Arduino designs. The simple designs are based purely on a gearmotor and some switches so this is no problem.

Actually, you want a Pro Mini rather than a Nano as you do not want resting current drawn by the USB interface either.

Tanks for your answer,

I follow your advice: I will use four AA batteries.
I removed the regulator.
I added an "on / off" switch.
For the control switch, all the useless boxes that I have seen use pin D2 with the interrupt mode.

is my schematic better?

You have not heeded this have you?

Also why not make the power switch to the whole thing the switch the Arm turns off

So you have been seeing a lot of useless circuits then, there is no need to use interrupts in this system.

Well, because the arm would not complete its retraction. :astonished:

This link and a few that follow shows a version of a Useless Box project.

The schematic below might give you some hints on what’s necessary.

The RTC and BubbleLicious are not fitted.

The relay was used rather than the P channel MOSFET.

And therefore a latching relay needs to be incorporated.

That depends on how you design your mechanics doesn’t it?

You don’t actually need any processors to make a useless box.

Welcome to the community.

As for your schematic it is fully functional. Good work !

I don't look at some of the design decisions as wrong however many feel there are better choices which usually come with experience.

For a useless box, it will function. However as noted by other posters (above) it will likely use batteries faster than need be.

For instance, R1 will work fine, however the processor has the ability to do the same function with an internal "resistor". This will eliminate R1 and the V+ wire to the switch. The switch will now be grounded or Open.

Well, no. The arm does not "snap" back, it is powered back in and the lid closes smoothly, so it has to be driven back under motor power.

The basic version uses a reversing switch arrangement. The forward direction is implemented by the main switch on the top of the box, when the arm cancels it, the motor reverses and drives the arm back until it hits the internal limit switch, shutting off the power completely.

If you want other actions, then you have to arrange an alternative power switch as Larry mentions.

Thank you all for your advice. I will study all this information and try to improve my project taking all this into account. I will come back to you when I have improved all this (I have a lot to learn from you) .

Thank you !