I want to make an HP illuminating wand - is this the right approach? - Page 1
Forum section: electronics / beginners

author: RepairedBySimonH
author_rank: Newbie
timestamp: April 26, 2019, 11:52:38 am
content: I am very new to electronics in general but have been becoming more interested in repairing things over the last year to learn how things work and have managed to repair a fair few things. Up until now I have never really been interesting in making things and designing circuits, however, my 6yr old son is very into Harry Potter and I saw the HP illuminating wand which looks cool as a torch but I think the price vs plastic quality of it cannot be justified so I am wanting to make my own version for his birthday in October (plenty of time) and use this as an opportunity to learn more at the same time.The wand is shown here -- but the basic principle is you wave the wand and it turns on and then you wave the wand and it turns off (i'm not really interested in the dimming option, I guess this is some form of specific IC).From what I've researched I don't believe there is a single component that can basically "switch" like a toggle switch would and I assume that there must be a circuit of some sort. I've researched far enough to guess the basic principle behind it might be a latching circuit with a switch based on movement, however being completely inexperienced I have a few questions about the best way to proceed.1) Is my basic theory right, or is there an alternative (simpler or better) option to achieve the same design goal?2) What type of sensor would be best? a basic vibration switch (e.g.https://www.adafruit.com/product/1767) or would something more fancy like a three-axis accelerometer sensor be more effective (although I have no idea what type of spec would be suitable, or how to go about selecting the right one). Or is there something else which could be better?3) Is it possible to get the latching circuit element in some form of IC rather than building from capacitors and transistors in the traditional way - if so any suggestions on keywords to look for? I have seen a YouTube video where it seems that a 555 IC could be used in this way but not really sure??4) Is there anything I should be particularly mindful over?I am wanting to make the circuit as small as possible so the wand can look elegant and doesn't have to be too thick (one of the things about the commercial product I don't like is how clunky it looks) so I am looking for small SMD type components where possible as I am happy using hotair for SMD rework soldering so any suggestions you have on actual components would be appreciated.Thank you in advance.

author: CJay
author_rank: Super Contributor
timestamp: April 26, 2019, 01:27:32 pm
content: Oh there's a whole bundle of stuff there, you can probably achieve all of it with a fairly simple microcontroller but it's going to be a steep learning curve

author: RepairedBySimonH
author_rank: Newbie
timestamp: April 27, 2019, 05:54:37 pm
content: Cheers, happy with steep learning curves - they are the fun onesWhen you say this could be achieved with a "simple microcontroller" what precisely do you mean? how would a microcontroller help - would this involve a level of programming? Last time I programmed it was along the lines of10 PRINT "HELLO WORLD"20 GOTO 10

author: amyk
author_rank: Super Contributor
timestamp: April 27, 2019, 06:45:48 pm
content: Around here, "HP" usually means something else... so I was a bit puzzled for a second and it made me click the link to read the threadThe price is indeed extremely high for the amount of complexity, but I guess 99.9% of it is just royalties... otherwise it looks like somethingbigclivedotcomwould review, teardown, and completely reverse-engineer.It will almost certainly be based on an "anonymous 8-pin microcontroller" driving a MOSFET to control the LED, with something likehttp://www.inertiaswitch.com/Products/Acceleration-Switches-1/Miniature-PCB-10/for the waving action. (I really hope they did not use a MEMS accelerometer, since those are far more fragile.)You could use one of the ultra-cheap Padauk microcontrollers discussed in other threads here. The code would be very simple, basically debounce the motion switch and change the state of the MOSFET driver output. If you want the intensity control you can use PWM for when it's on.