Build a quiz board that indicates right answers AND wrong ones

Thread Starter

gable74

Joined Mar 23, 2016
60
So assuming they go for this option, it looks pretty easy to integrate into the design with one caveat, it requires ground signals to trigger the sound file. The way I have it now it would provide positive voltage rather than ground. How can I convert each positive signal (16 of them) to a ground signal without using a boat load of relays?
 

Thread Starter

gable74

Joined Mar 23, 2016
60
Well, they like the idea of the sound board....:rolleyes:

So unless someone has another suggestion I am just going to build a 16 channel relay board to convert the positive signals to negative and output those negative signals to the sound card in order to play the sound files. Something like the schematic attached. I did not bother drawing out the relay card since its a fairly straight forward setup to do the + to - conversion but I will be happy to do so if someone wants to see it. I really hope this is the last revision......:p
 

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crutschow

Joined Mar 14, 2008
34,285
The problem is, the sound will occur when the Ans pen is connected, whether it's a correct answer or not.
You could connect the sound card power or the speaker through the correct answer (green LED) (DPDT) relay so it only sounds for a correct answer.

Instead of relays to invert the signal you could use a resistor and a transistor as shown below:

upload_2016-3-31_11-59-6.png
 

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Thread Starter

gable74

Joined Mar 23, 2016
60
The problem is, the sound will occur when the Ans pen is connected, whether it's a correct answer or not.
You could connect the sound card power or the speaker through the correct answer (green LED) (DPDT) relay so it only sounds for a correct answer.

Instead of relays to invert the signal you could use a resistor and a transistor as shown below:

View attachment 103494
Okay I see that now. I would prefer switching the speaker lead I think. If I switch the power to the sound board it may be delayed by a "boot-up" time or something.

I am sort of new to anything more than simple electronics and I have never seen that method of switching polarity. I would need to do that with each positive lead correct?
 

crutschow

Joined Mar 14, 2008
34,285
....................
I am sort of new to anything more than simple electronics and I have never seen that method of switching polarity. I would need to do that with each positive lead correct?
Yes, you need one transistor and resistor per answer lead.
The NPN transistor turns ON when a positive current goes into the transistor base lead and this basically connects the collector lead to the emitter lead with a very low resistance, giving you the "ground" signal you need to turn on the sound card.
With no base current the transistor is OFF with a very high resistance between the collector and emitter.
 

Thread Starter

gable74

Joined Mar 23, 2016
60
So just to try and wrap this up, I am going to cut the ground to the relay inverter card with my DPST relay that operates the correct answer light. That way no ground will be available to invert the signal if the wrong answer is selected. I do not have access to the transistors locally to build the inverter as shown by crutschow, but will try that method on the second box once this one is complete. Attachment #1 shows my final design and attachment #2 shows the inverter relay board if anyone wanted to see how I was wiring it up.


Thanks for the help Crutschow!
 

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GopherT

Joined Nov 23, 2012
8,009
Well I found this which looks like exactly what I was talking about. It has 20 channels, triggered by individual Neg(-) signals. Signal (1) plays file #1, signal (2) plays file #2, etc. Only problem is its $75. I don't think the Ranger group will want to opt for that costly of an upgrade. If anyone has any other outlets for cheaper solutions let me know.

http://www.amazon.com/Channel-Sound...e=UTF8&qid=1459433915&sr=8-1&keywords=FN-BC20


Thanks,
Sounds like fundraiser time or Sponsorship time.
 

Thread Starter

gable74

Joined Mar 23, 2016
60
How about a couple of ULN200x series parts for the inversions. You have the common 7 channel and the 8 channel versions.

e.g.http://www.st.com/web/en/resource/technical/document/datasheet/CD00001244.pdf

There are lots of ULN2003 breakout boards. e.g. http://www.electrodragon.com/product/stepper-motor-driver-uln2003-board/

I did not totally address the suitability.
Could you elaborate how these would work? I do not have an advanced electronics background, generally just simple circuit stuff.
 
These are "essentially" crutschow's driver circuit. The 2003 is 7 circuits, not 8, but it's a really common part.

What it also contains is freewheeling diodes because the chip was designed to drive relays. DC coil relays should have a reverse biased diode to absorb the collapsing field when the relay is de-energized. This "protects" the other electronics including the power supply.

The chip only needs ground to operate UNLESS your driving a relay coil. Then the COM pin is connected to the relay power supply.

So, you might have to learn to make a connector. If the LEDs are a problem, you can always cut them out.
the point is that the boards may be readily available.

The ULN2803 is an 8 channel version. https://www.sparkfun.com/products/312

You can easily breadboard this as well, but I really would suggest connectors. This means researching a crimp tool and using the right size wire.
 

Thread Starter

gable74

Joined Mar 23, 2016
60
Okay thanks. The loads on this thing are really non existent. The light bulb loads are relayed from the power source and wont effect the circuit.

So seven/eight separate circuits within the one chip? So I could come in with seven separate 5v leads and come out with seven separate grounds? So I would only need (2) of these chips for what I am doing?

Sorry, I guess what I am asking is how would this be wired to do what I am trying to do?
 
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7 or 8 inputs to 7 or 8 outputs depending on the chip. The chip also needs a ground.
So, yep 2 to 3 chips.

It's just that the 2003 is more common. You could even get them at Radio-Shack.

You could also use these: http://www.winford.com/products/dta35.php for breakouts. They would use nice and familiar screw terminals.

It COULD also introduce you to DIN rail construction. DIN rail is an electron's erector set.
 
I want to point out something though, wire is available with two different strandings and sometimes it's important.

Some Terminal blocks have "wire protectors" and others do not. "Wire protectors" ensure a flat piece of metal clamps the wire instead of splitting the ends. Wire ferrules http://www.digikey.com/product-sear...t=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25 essentially accomplish the same thing.

They are made of a soft metal tube (No crimping tool required) that goes over a stranded wire. They come in insulated and non-insulated versions and some will allow two wires to use the same point.

A lot will depend on HOW you construct it. Like whether or not you have to stand on your head to troubleshoot it.

You could put it all in a box with at least two connectors that attach to your display.

Rows in one connector and columns in another.

You have DC, buzzer and an answer LED bulb

So pulling those connectors make it easy to troubleshoot. Your box could have a power led and an answer LED too.

I made a LOT of work stuff using CPC connectors. e.g. http://www.digikey.com/product-sear...t=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25

You had, a choice of 4, 9, ? and 37. But you have to buy everything separate. You have to understand same sex and reverse sex versions.
The $20 USD tool made removing pins a snap.

The crimping too has gotten pricier and so have the connectors. The cool part was everything but the pins were re-useable. I made such modular stuff that whatever I made stayed intact.

The circuit is one thing, the power supply another, ability to troubleshoot yet another, the documentation is yet another.

So,let's say it's kept under a closed panel at the bottom of the display. Let's say you could remove it by unscrewing a few connectors and troubleshoot it stand-alone. Or maybe you could extend it to put it on a table.

These are all options, but they all cost.

What about a 1/2 rack case on slides with a lock?

BTW, I tend to design stuff at a higher level and then cut.

The actual cool part of using two CPC connectors is that you can simulate answers with a "wire" without a board.
The actual controllers would all stay wired the same way and you really "could if you wanted to introduce a short segment of 2 connectors that become the answer key.

So, if you had multiple boards, you could swap controllers.

The what if becomes:
What would it take to make the other board work like this new one?
How easy is it to change the answers?
This one is broke. Can we use the other controller?
We want another row. How easy is it to expand?

Those kind of questions come in when you ask:
A. If I had all the resources and infinite money what would I like?
B. Then ask; What must I absolutely have?
C. and finally Is there anything I can do now (cheaply) that gets me closer to A.

It might even be running unterminated wires
It might be selecting a slightly different amperage power supply
It might mean a slightly larger case.
 
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