Autism electronic sensory box

Discussion in 'General Electronics Chat' started by Deputyduke, Apr 24, 2019.

  1. SamR

    Active Member

    Mar 19, 2019
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    As to the switch that you have. It is a latched/maintained ON - OFF - ON DPDT switch. Usually used to select between two of four devices and OFF. It is also designed for spade lug connectors. Not screwed or soldered connection, but a crimp onto the wire female lug for the spade connector on the switch. It is super heavy duty and is rated for 250V AC 10A/12V DC 20A. Quite a bit of electrical overkill, but extremely rugged/childproof. The spades are individual. Meaning that the two on each end are for different electrical connection as are the 2 in the middle. Each end spade is for a separate device and the middle spades are the common supply voltage for the spades on that side. Power supply + to middle spades, each end spade to a separate device. You can use each end for two separate LEDs, but only one end at a time. Center position is OFF, either end is ON for the selected devices connected to it. That switch will operate 2 separate LEDs from each end if all lugs used. You do not have to use all 6 spades if you only want one LED from each end, just use the 3 spades on one side.
     
    Last edited: Apr 25, 2019
  2. Deputyduke

    Thread Starter Member

    Apr 22, 2019
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    Many thanks will a standard 5mm led support 10mA?

    Reason I ask is that the guy i bought them from on ebay told me that they run on 0.02mA
     
  3. Deputyduke

    Thread Starter Member

    Apr 22, 2019
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    Sorry folks just seen your previous message

    The 20mA is the max the led can take so in theory i could pick a resistor to run the led at 5mA?
     
  4. dendad

    Distinguished Member

    Feb 20, 2016
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    Try 5mA and see if it is bright enough. I never run indicator LEDs at 20mA. Usually well below 10mA is quite ok.
     
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  5. SamR

    Active Member

    Mar 19, 2019
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    Yes. 220 Ohm is a good start. Got up or down to adjust the brightness level you need depending on ambient light. I use 560 Ohm for 5-9V with the LEDs I use. More resistance, less current, dimmer LED, longer battery life. Also, different colors have different brightness levels so you might tweak for that. http://www.gizmology.net/LEDs.htm
     
  6. Deputyduke

    Thread Starter Member

    Apr 22, 2019
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    Excellent so i reckon a resistor of 264ohms??

    Battery pack = 15v
    Led voltage drop = 1.8v (red)
    Current =5mA

    Am i correct?
     
  7. SamR

    Active Member

    Mar 19, 2019
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    Yes, close enough. And that is for each LED. Add it up if more than 1 LED on at a time.
     
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  8. SamR

    Active Member

    Mar 19, 2019
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    R=V/I so R = 15/.005 = 3000 Ohms It will drop 1.6V but you are supplying it with 15V.
     
  9. SamR

    Active Member

    Mar 19, 2019
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    15V/1.8V = 8.33 which is the number of LEDs the power supply can light at the same time.
     
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  10. Yaakov

    Well-Known Member

    Jan 27, 2019
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    Given the purpose of this device I have two comments. First I echo previous comments that the choice of power source is a mistake. It is a low capacity, expensive battery and 12V is not required. A 3V source, such as two AAs would work well, last far longer, and be cheaper. Using 3 or 4 NiMH rechargeable AAs would be even better, which brings me to my second point.

    While I realize you are just learning, there is a potential problem with this device that needs consideration. If the LEDs are left on, the battery will be dead in a very short time, and it seems quite likely that it will get left on. Ideally, you would have a timer that shut it off when it was idle for a certain time, but, you are struggling just to get switches and resistors wired to LEDs, so that’s not reasonable.

    However, please consider a “master switch”. If you had one switch that enabled and disabled the entire box it would be easier to be sure it was off. This switch could be placed in the common wire going to the negative supply, and that way it would deprive all LEDs of power when off. Eventually, a timer that did this for you would be best.

    Good luck, once you get the hang of this it will seem a lot easier.
     
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  11. dendad

    Distinguished Member

    Feb 20, 2016
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    I like the master switch idea. And if you make it a non locking push button, it will need to be held on to light the LEDs.
     
  12. Deputyduke

    Thread Starter Member

    Apr 22, 2019
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    Lads, once again thanks so much your information and tips have been invaluable to me

    To be honest, I am useless with reading electronic scehemditic diagrams,

    Therefore in my simple minded lay-man terms, I have uploaded a rough mock-up drawing of my sons sensory box

    Taking into account, the invaluable information you lads have advised me with so far and your drawings, could I please be cheeky and ask any of you to draw me a very rough lay-man terms wiring diagram for each of the components on my silly drawing.

    It will now be powered by a 10 way AA battery holder

    The master on/off rocker switch will be salvaged from an old PC power supply I have

    Lads, once again thank you so much for all of your help

    I really am truly sorry if I have asked you this info before in different steps, I realise I am prob trying to run before I can walk

    Would you believe my 12 year old daughter actually offered to help me solder the bits as she is currently learing that in school!

    Embarrasing I know!

    Thanks a million in advance

    Glenn

    (PS: Please in my kindest way do not upload an electronic schemtic drwaing as I will really really struggle to understand it, I basically need to see what wire goes to which pin on each switch / button / rotarty switch and LED, a massive ask I know and I really do hope that one day I can re-pay the favour)

    :)
     
  13. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
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    There is one missing piece of information needed. What is the current required for each LED? I can guess for most of them. There are tables of typical current requirements for each color. Butit would be s guess.

    Where did you get the LEDs? If you bought them online, a link to where you bought them would be useful.

    Otherwise, I will take a shot... we can fill in the missing info later.
     
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  14. Deputyduke

    Thread Starter Member

    Apr 22, 2019
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    Many thanks, I just bought bog standard 5mm LEDS from a guy on ebay (Aint arrived yet)

    I asked him for a datasheet, but he told me that he buys in buld from china and that they are "bog standard" 5mm leds with a voltage drop of approx 2v and 20mA current

    (I cant vouch for this as I don't know myself!)
     
  15. dendad

    Distinguished Member

    Feb 20, 2016
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    LEDBox.jpg
    Another thing you can do, use an "RGB" LED as well. That has 3 LEDS in one package so then different colors can be made, depending on whet LEDs are lit.
     
  16. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
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    That’s enough
     
  17. dendad

    Distinguished Member

    Feb 20, 2016
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    RGB LED...
    https://www.ebay.com.au/itm/100-pcs-5mm-4-pin-RGB-LED-Common-Anode-Red-Green-Blue-Y3F7/253498135048?_trkparms=aid=555018&algo=PL.SIM&ao=1&asc=57481&meid=7bf6763070814b51aaaea84b6ddebb43&pid=100005&rk=3&rkt=4&sd=253626697920&itm=253498135048&_trksid=p2047675.c100005.m1851

    a2b84fd-led_pinout.png RGB.jpg

    Make sure you get "Common Anode" for this connection setup. "Common Cathode" will work too, but the battery polarity will be reversed.

    And, depending on how keen you are, multiple switches and resistors can be used on each LED part to allow more color variation. The trick is deciding where to stop ;)
     
  18. dendad

    Distinguished Member

    Feb 20, 2016
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    Here is a quick circuit. I know you said no circuits, but look at this and see it is not much different to the drawing.
    I have shown 3 pushbuttons for one LED, the other 2 LEDs also have the same circuit but I could not be bothered drawing it 3 times ;).
    This setup will potentially give 512 colors!
    The trick with the resistors is to select the resistor value for the max current you want, then double the resistance for the first resistor, double again for the second, double again for the third.
    This is a basic Digital to Analog Converter (DAC) and these sort of things are very widely used.
    9BitRGB.jpg

    Really, the resistors may well start at 4K7, then 8K2 and lastly, 18K. The values I have are probably a bit on the low side for 15V
    Also, the resistors can be all the same value but one for the first LED, 2 in line for the second and 4 in line for the third.

    As you can get pushbuttons very cheap on Ebay, 9 buttons, 9 resistors and one RGB LED would not take to much to build.
    Try not to get the LED chip too hot when soldering. Keeping the leads long will help. Slide some plastic tube, commonly known as "spaghetti", over the bare leads and solder joint.

    Even using just 2 switches and the resistors for each LED will give you "6 bits" or 64 colours. Oops, "colors". My other spelling gives a hint to where I live ;)
     
    Last edited: Apr 26, 2019
  19. spinnaker

    AAC Fanatic!

    Oct 29, 2009
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    Cool that you want to do a project especially for your son. But have you thought about a phone app? Bet there are lots out there probably designed by psychologists. Maybe use that till you get your custom device online?
     
  20. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
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    Does “10 way AA Battery Holder” mean that it holds 10 AA batteries?

    Way too much power. You only need 4 AA batteries for this project. Ten batteries would have to waste more than half of its capability and could damage the LEDs.

    You will also need to obtain some resistors. It looks like you will need two different values. 1/8 or 1/4 watt resistors will be fine. Don’t worry now what that means. I mention the Watts because you will see it when you look for resistors to buy.

    As I remember, all of the switches except for the toggles have two connections. The toggles have six. That’s ok, we won’t use four of them. I drew a picture showing you which two connections to wire to. In the case of the switches, it doesn’t matter where each wire connects.

    In the case of the LEDs, it does matter which wire goes where. An LED has one long lead and one short lead. I mark which one to use on the diagram.

    I show wires attached in the middle of another wire in several places. You can remove the insulation along a wire or just piece short pieces together. These joints need to be insulated. You can get some heat shrink tubing or use vinyl electrical tape.

    I’ll attach the picture later. I just wanted to give you a heads up. AND please reply with the answer about the battery holder.
     
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