I need a critical help in designing a magic toy - Page 1
Forum section: electronics / projects

author: salvazero
author_rank: Newbie
timestamp: January 12, 2017, 01:12:55 pm
content: I want design this project for magic shows, and I would like to include this in the act.How Can I design a circuit so I can make the ball move? I need to design circuit for it.The wand will have the transmitter.The ball will have the receiver in it.I want to make it stop when the wand is less than 1 feet away and or plus 2+ feet away.Start at 1-2 feet, spacing is not critical. Close is good enough. Parts I think I need.The Wand1. An adjustable transmitter2. Battery The ball1. A receiver2. Motor-is not included in the circuit3. Battery4. Gears- is not included in the circuitI need for you to advise me on what is the best way to make this magic toy. I just need the circuit without the motor or gears.See the example attachedThis is an example onlyI need a correct circuit for it.1. I need a transmitter to transmitter only at a distant of 1-2 feet only. I was told that I would need an adjustable transmitter and Receiver.2. I will be removing the on and off switch in the ball and replacing it with the receiver, to tell it to come on or off. The receiver will open and close the circuit for the battery to activate the switch.Can you supply me a schematic showing me the wires to connect and what type of transmitter and Receiver to buy and any other components that I might need to complete the circuit?I want to know Schematic showing me the wires to connect and Parts I will need.Any help will be appreciated.Thanks in advance

author: Marco
author_rank: Super Contributor
timestamp: January 12, 2017, 02:42:47 pm
content: Quote from: salvazero on January 12, 2017, 01:12:55 pmThis is an engineering project and it's not terribly simple either, unless someone solved the exact problem and was nice enough to release it you'll have to do some engineering. Getting the ball to roll away in a straight line from the wand regardless of orientation requires accurate distance and orientation measurement, which is a hard problem.Would it be acceptable to use a transparent plastic ball and paint it with some IR transparent paint? That way you could use the IR intensity received at multiple photodiodes to guestimate the distance and direction of the wand.If the ball is essentially ultrasonic transparent, ultrasonic distance sensors might also be an option.PS. one rotating photodiode/ultrasonic sensor might be better, the gyroscopic effect might keep the detector stable and horizontal while the ball is rolling which would prevent some problems.

author: CJay
author_rank: Super Contributor
timestamp: January 12, 2017, 02:50:25 pm
content: Quote from: Marco on January 12, 2017, 02:42:47 pmNope, it's really simple unless he wants to be able to steer the ball and even that isn't difficult.He's already got a schematic for the HT12, just hide the transmitter in the wand with a hidden switch to activate it and a couple of tilt sensors, press the button to turn on the motor, tilt the wand to steer.Inside the ball you have a receiver that controls the main motor and a steering motor.

author: Marco
author_rank: Super Contributor
timestamp: January 12, 2017, 02:53:07 pm
content: He didn't say he wanted a remote control, he wanted it to move based on the distance of the wand and away from the wand.A remote control makes it easier, though the magician would have to be very careful about how he puts the ball down so it rolls in the right direction. Especially since you don't want to put markers on the ball which the audience can see.

author: CJay
author_rank: Super Contributor
timestamp: January 12, 2017, 03:24:48 pm
content: You're right, so they could build in a series of proximity sensors in different axes and have the ball sense the presence of the wand but that gets complicated really quickly and we're talking to a beginner.Much simpler to have a hidden button (even perhaps one in a separate box to inhibit/allow movement so the audience could participate) and a couple of tilt sensors in a wand activating different inputs on the HT12 already shown, as for predicting the direction, yes, the ball could be marked in many ways which aren't obviously direction markings, many children's play balls are already printed with pictures or patterns for instance, or they could just watch which way the ball rolls and steer accordingly.

author: salvazero
author_rank: Newbie
timestamp: January 12, 2017, 03:26:05 pm
content: Thank you very much CJay and Marco for your time and consideration.The drawings was just an example. I need to make it activate with an RF signal 1- 3 feet away (This is a constrain). Accuracy is not important, just as long as it operates when the device is near it. I don't mind the size of the wand, I can work around that, the magician can put the transmitter under his sleeve.Here is how I think about it so far:For the TX (wand)I will have three main parts:1.Infrared Proximity Sensor - (Sharp GP2Y0A21YK) to measure the distance.2.Control Circuit: Which is comparator to detect when the distance become 1-2 Ft3.RF Tx: To transmit a control signal (One or Zero) to the RxFor the RX (The ball)I have also 3 main parts:1. RF Rx2. Control circuit (Motor driving circuit)3.MotorAnd this how it should work:-Infrared Proximity Sensor - (Sharp GP2Y0A21YK) reading ranges from 0.4 volts at 80 cm to 3 volts at 10 cm.-I should make the comparator output Logic 1 when the distance become less than 60 cm (2 Ft.) so that the comparator will output 1 when the input voltage coming from the sensor is greater than or equal 2 V and output 0 otherwise.-Then this logic 1 will be sent through an RF signal to the ball.-The driving control circuit in the ball will turn the motor ON when it receive this Logic 1.Kindly, tell me whether this approach is correct or not.

author: PA0PBZ
author_rank: Super Contributor
timestamp: January 12, 2017, 03:51:22 pm
content: Quote from: salvazero on January 12, 2017, 03:26:05 pmHow does the ball know which way to go, or is the wand always approaching the ball from the 'back'?

author: salvazero
author_rank: Newbie
timestamp: January 12, 2017, 04:14:50 pm
content: Yes PA0PBZ, the wand always approaching the ball from the back.Actually I still confused about the parts I need to get this project done.

author: Marco
author_rank: Super Contributor
timestamp: January 12, 2017, 06:53:34 pm
content: I think you have exaggerated expectations of the ease of this project.This hasn't even gone into the mechanics, look here how a naive approach to the mechanics of a simple light following ball robot has a ton of instability for instance :Now you could start with something like the Sphero Spark+, which will give you a relatively good sphere robot mechanically. Interfacing with those existing electronics then becomes a non trivial exercise. Interacting with it on the hardware level will require a ton of reverse engineering. Or your additional electronics in the sphere could communicate with a phone through bluetooth, which would then proceed to control the Spark+.None of this is easy IMO. Especially not if it has to look smooth and slick.