Circuitry for a dollhouse

[Pixmusix]

Linking from

Transistor Pack (170 pcs) (FIT0322)

Clever. I have a paper copy I can refer too. Nice! I actually have a plan and a schematic. I might actually start a stand alone thread for it if your curious or have some feedback. You can find that below.

@Robert93820 here is my plan to use a single push button to latch the lamp. I’ve got a jk flip flop to handle the latching and my button is just a clock that’s flipping and flopping Q and Q-.

The button here is this tiny jaycar button. It’s max is 12v so I could use it in series with the lamp but I felt that would be flying too close to the sun. I need 5v circuitry anyway for my LS series ICs.

[Pixmusix]

Hey @Robert93820
Wondering if you can improve this idea a little.

I’m glad this circuit is working.
However it would be ideal if the lamp could be on the other side of the transistor.

Imagine wiring this house. As it stands each lamp would need it’s own return path to the transistor.
However if the lamp was on the other side of the transistor all the lamp’s returns could combine at ground. That would making wiring the house soo much easier which is good because we have to work with conductive tape.

I looked at using a PNP transistor because that would put the collector and thus the lamp towards ground. However I think I’d be tying the base to 12v and so my 74ls73 would need some kind of voltage protection. It all got away from me so I settled for the NPN design I felt more comfortable with.

Maybe I gave up too soon?
Any better ideas?

[Robert93820]

Hi Pix

@Pixmusix

I looked at using a PNP transistor because that would put the collector and thus the lamp towards ground

Not quite correct. The lamp will drop 12V so you would have one side of the LAMP at ground but everything on the other side would be something like 12V above ground.
That IC is only good for 5.5V so I think you are stuck with NPN switching to ground. You can’t have the lamp in the emitter circuit as then the base would have to go to about 12.6V to turn it on.

I don’t think the wiring is any worse off this way. You either common all the grounds as you suggest and return that to some common point or you common all the lamps on the one side and return that to 12V. Same amount of wiring. You will need a transistor with a healthy hfe as I don’t think this IC will source much current.

Keep it simple.
Cheers Bob

[Michael99645]

Just a thought here, and I am more then happy to be wrong Depending on the quality of the push button, you will get some level of “bounce” as it makes contact, breaks contact many times as its getting pressed down. As such, the JK may clock more then once per press, resulting on the lights may be on may be off. By adding a capacitor in parallel with the 10K, should give a power reserve to hold it High for an extended period.
i.e. Rapid charge when button makes contact, then slow discharge via the 10K resistor when the contact is broken. So any rapid contact/no-contact could be absorbed by the cap. (or is there some level of anti-bounce in the JK?)

[Pixmusix]

@Robert93820

That IC is only good for 5.5V so I think you are stuck with NPN switching to ground. You can’t have the lamp in the emitter circuit as then the base would have to go to about 12.6V to turn it on.

Yeeeah gotcha. 0.7v rule.
Ah well. NPN it shall stay.

@Michael99645

t/no-contact could be absorbed by the cap. (or is there some level of anti-bounce in the JK?

Ah good catch. I totally forgot to debounce.
Some kind of rc debouncing like suggested will work. I’ll intergrate it.

[Pixmusix]

From

Transistor Pack (170 pcs) (FIT0322)

Hi Pix Just did a bit of research. Try the 74HC73. No one lists a max and min output current but the absolute maximum ratings are given as +/- 25mA. (sink and source) which gives you a chance of a few mA to drive your transistor. You might even go lower than 3k3Ω to make sure of switch on. If you have source trouble Jaycar stock these. Cheers Bob

@Robert93820
Reading the datasheet on the 74LS74 I have 20ma which I’m hoping is enough.
I already have these so I’m keen to use them up.
If they don’t work I’ll source some 74HC73s

[Robert93820]

Hi Pix
I draw your attention to the line “high level output current” below

Straight from TI data sheet.
Cheers Bob
one more thing. The 74lLS and HC73 are J/K flip flops with different logic that the 74LS74 which is a D flip flop and does not have a “toggle” set up as does the '73 so won’t work as you expect.

[Pixmusix]

Ah ok. I was reading this table here.

I wonder what the difference between recommended operating conditions and electrical characteristics [in] recommended operating conditions is supposed to be.
Weird.

I actually failed to note that the measurement for Iih is in ua not ma so even so it’s tiny.

I think I need to measure

P.S. I have a few 74HC74s lying around so I can try those as well.
I can buy more if they’re joyful

[Robert93820]

Hi Pix

@Pixmusix

ave a few 74HC74s lying around

As I said above, different flip flop and I am not sure if they are even pin compatible. I think VCC and Gnd might be different for a start. Please check before powering up.
Cheers Bob