Building a board of buttons/switches/etc.

[KE5KBG]

I would get a large AC to DC transformer instead of a battery. That way he won't run it donw and it won't cost as much for all the batteries. Or find an old plug for a calculator or anything, you could use led with the lower voltage. You could get one of those electronic project boxes where he won't be pulling the wires and everything is enclosed.

 

[cpgoose]

I would get a large AC to DC transformer instead of a battery. That way he won't run it donw and it won't cost as much for all the batteries. Or find an old plug for a calculator or anything, you could use led with the lower voltage. You could get one of those electronic project boxes where he won't be pulling the wires and everything is enclosed.

I have 2 things at the moment (on my desk): One is a power cable from a gateway laptop, and the other is a computer power supply. I remember in college we used to hook-up a car amplifier into the computer power supply and plug it into the wall so we could use it in the dorm (only a few times, though). Could I use one of those two items to power this?

 

[Andy1845c]

You could use the computer power supply, but its kinda big isn't it?

I can't say if the laptop cord would work or not without more info. Is there any ratings on it? Output voltage and current?

 

[picasm]

I have 2 things at the moment (on my desk): One is a power cable from a gateway laptop, and the other is a computer power supply.

I think you could just use battery power, all you need to do is build-in a timer (using a 555 chip) so that it turns itself off after about 5 minutes.
Turning it on would be done using a pushbutton press to start the timer,then it cannot be left on permanently.

 

[cpgoose]

Yea, I guess the computer PSU is somewhat big.

The laptop cord has a plug, what looks like a fuse, and then a black box piece. It says:

Gateway Model # ADP-50FB
AC Input: 100-240V AC, 60/50Hz 1.5A
DC Output: 19V 2.64A (with a line w/3 dots under it in between those two numbers).

 

[Andy1845c]

The gateway cord would work to a point. You need to decide exactly what is going to be on this board and how much current it will draw with everything on at the same time. The decide on how to power it and at what voltage.

With the cord, your going to want a voltage regulator in the circuit. It says the output is 19 volts, but with less then the rated current running though it, the voltage will be higher by quite a bit. And with the current draw constantly changing as the child plays with the various buzzers and lights, the voltage will be all over the place and make it hard to size resistors for your LEDs.

 

[Mad_un]

Hey, can you elaborate on the LDR? I'm not sure what that is, besides what you said about it working when you put your hand over them. I tried looking on Jameco, but I guess I'm looking in the wrong spot. Great idea!

Like andy1845c said, an LDR is a type of resistor. However, unlike a conventional resistor which has a relatively fixed value, an LDR’s resistance changes depending on the intensity of light hitting it. It can be used in conjunction with several other components to produce a circuit (ill find and example later) which senses the intensity and triggers an output where appropriate.

Here is a LDR **broken link removed**

A draw back I just thought of though is, because it will be sensing a lack of light, it will turn on at night if the lights aren’t turned on.

 

[cpgoose]

Ok, can I just make sure I'm on the right track here? I've done more research, etc, and I'm starting to doubt that this can be done without having a massive power supply (like a computer PSU).

Let me just start basic (see attached). Let's just say I have 4-AA batteries connected as power (and they're 1.5v each). Then, if I use these LEDs (see link below) which say they're 2.0v, would this diagram work ok?

https://www.radioshack.com/product/...orePrice-RSK&x=4&support=support&tab=features

 

[Nigel Goodwin]

No, because the batteries are in parallel, giving only 1.5V - it's also ABSOLUTELY ESSENTIAL that you have current limiting in series with the LED's, like a resistor.

 

[cpgoose]

Ok, so if the LEDs were only 1.5v, then this diagram should work since my power source is putting out 1.5v, right?

And can you expand a bit on the resistors? Would I have to put one before each LED, or just 1 before the set of 4? I'm assuming this is to make sure they only receive a max of 1.5v and no more?

 

[Nigel Goodwin]

Ok, so if the LEDs were only 1.5v, then this diagram should work since my power source is putting out 1.5v, right?

And can you expand a bit on the resistors? Would I have to put one before each LED, or just 1 before the set of 4? I'm assuming this is to make sure they only receive a max of 1.5v and no more?

LED's are fed with current, not voltage, the resistor is to limit the current to the value you want. You need a resistor with each series chain of LED's.

 

[Stellarcore]

When I was a kid, my dad made me something very much like this. It was really cool and I spent many hours on it. It's probably the single biggest thing that made me want to get into electronics.

If I recall, my electronics box (or whatever you wanted to call it) was enclosed in a wooden frame with a plexiglass top; this see-through top is imperative to make the child wonder about the stuff inside. The top would also simply slide out when one end of the wooden frame was removed (ie, there were grooves on the top edges of the wood). This is also a good thing to do because as the child gets older, it means that he/she can easily open up the box to make modifications to the stuff inside.

My box was split into two main sections. One section was a low voltage side that ran from a 6V wall wart, the other was a 12V side that ran off of another wall wart. The 12V side was fused. On the 6V side, there were a few different things to play with, including some LEDs, a basic audio amplifier, and a basic frequency generator.

The frequency generator was just a 555 timer with a bunch of different resistors hooked up in parallel with push buttons. There was also a potentiometer in parallel. The output of the 555 would go directly to a speaker that was mounted under the plexiglass (with holes drilled to let the sound through). The result is that when you push the buttons and play with the pot you can get different tones out of the speaker.

The audio amplifier was hooked up to the same speaker through a spdt switch, and it has just a simple pot to control volume. It would be neat to also add some active filters/amps that could be used to "morph" the sound from the mic.

The 12 volt side basically had one main feature; there were a number of RCA jacks that various things could be plugged in to. above each RCA jack was also a screw terminal (in case the item to be plugged in didnt have a male plug to fit the RCA jack). Each of these jacks had a rotary switch that was setup to switch the outputs on or off, in either polarity. There were also LEDs hooked up in each direction on the output so that one LED would light when the polarity is one way, and the other would light when its in the other direction. The purpose of these jacks was that you could get interesting electric machines to plug in to the board. Fun examples of stuff to plug in would be a vibrating motor (as someone mentioned earlier), a normal motor, maybe a small electric car with geared back wheels, an electric bell, an electromagnet, various incandescent lamps, etc..

 

[cpgoose]

Ok, help a newbie out here, what's wall wart?

Thanks for the post, you gave me a lot of ideas. Hopefully I can stick with this. I'm thinking of scrapping the idea because it seems that it might take too many batteries to run...unless I can figure out how to use the computer power supply or the laptop power supply.

Silly question: What's the difference between your car's 12v battery, and the 12v battery that you use for say a keyless entry remote?

 

[Nigel Goodwin]

Silly question: What's the difference between your car's 12v battery, and the 12v battery that you use for say a keyless entry remote?

POWER!.

What's the difference between an 18 wheeler truck and a moped? - same sort of thing!

 

[cpgoose]

I was looking for which term separates the two...AMPs?

 

[Nigel Goodwin]

I was looking for which term separates the two...AMPs?

Yes, either AMPS (current) or WATTS (power = volts x amps).

 

[Stellarcore]

Ok, help a newbie out here, what's wall wart?

Its a power adapter that plugs into the outlet. It takes the outlet AC and converts it to a smaller DC voltage (typically 6V, 9V, 12V, etc...). Each "wall wart" is rated differently, typically less than an amp.

It is definately the way I would power your box, its cheap and relatively safe. You can buy adapters new from many electronics places or, preferably, just scavenge it from a broken device you already have (ie cordless phone, chargers for various devices, etc..) Just snip off the jack from the end, figure out which wire is positive with a multimeter and add a new jack that fits a mating plug on your electronics box (its probably best not to leave exposed wires for a child to play with).