Circuits

[DaOld Man]

I thought I would open a thread with circuits that are simple and may benefit us in our passion to re-create the Arcade experience.

First up is a simple circuit using a 555 and a handful of other components to control either DC motor speed (one direction only), or LED brightness.
LINK)

The circuit above is designed to control a motor, but if you replace the Q1 with your LED, it can control the brightness of the LED.
The 555 integrated circuit is a very common timer. (Available online or at Radio Shack).
The one rated for 4.5 to 16 volts is good for 200 MA.
If your LEDs draw more than that, just use a suitable NPN transistor to switch the power to the LEDs.
You can use the exact circuit in the link above, but just swap the motor in the circuit with your LED (with the appropriate resistor for your LEDs.) The diode around the motor in the above circuit is not needed, if you are controlling LEDs.

Got any useful circuits that you think would help out the group?
Post them here. We all need inspiration.

Edit: Here is the above pwm circuit, modified to control LED brightness:

[pixel.arcade]

Very interesting, inspiration is a keyword!

[DaOld Man]

Here is a very good H drive which is pretty easy to make.
This is not my circuit, it is posted here, with a lot of info on how to build it.
Caution! I highly suggest you use heat sinks on the power transistors, especially if you use PWM for speed control. I fried the transistors on my first build, without heat sinks.
The circuit:

[ed12]

hi
interesting thread
i have always loved the 555
i did a google 1 day to find a 555 timer circuit
and came across 45 circuit's u build with 555
i did not book mark it but thought i would point it out

ed

[DaOld Man]

Here is a very handy circuit I made a few years ago. Actually it is a modified wireless doorbell. Using a cheap battery powered door bell, I made an extension to my current doorbell.
I needed it for upstairs because i had a hard time hearing the doorbell (which is downstairs) when I was upstairs working on my projects.
It would have been a nightmare to route a wire from the downstairs chime to an upstairs one.
I could have but you know a lazy man comes up with an easier way to do the job.
Its a pretty simple circuit and works very good, providing that you remember to change the batteries in the chime part.
I removed the small 12 volt battery from the button that came with the wireless door chime. I made a small circuit that rectifies, filters, and regulates the AC from the downstairs door bell solenoid.
Then I taped the button to always be on.
When someone pushes the outside button by the door, the downstairs door bell rings and the wireless button is energized, sending a signal upstairs and ringing that one too.
The zener I used to regulate the power is 8.1 volts, it is what I had in my junk box at the time. It really needs to be 12 volts. The 8.1 volts decreased the distance of the remote chime, but it was ok for where I placed it.
The diagram below really sucks, (I couldnt find my original, this is copied off my blog site), if anyone is really interested in doing this, I will re-draw it better.

[DaOld Man]

Most modern autos these days have either a beeper to tell you that you left your headlights on, or they automatically turn off after a few minutes.
But older cars probably have neither.
Back in the day, I had a 1988 Firebird, which had neither. One night I left the lights on and the next day the battery was dead.
So out of necessity, I came up with this extremely simple headlight minder. The hardest part of this is connecting it to your car.
I used an small electronic buzzer. The one I used was polarized, if you connected it backwards it would not work, which was just what i needed.
I connected it to the radio circuit to get the ACC, and to a parking light "hot" wire, that way it still works if I just leave the parking light on, and if I need the lights on, the alarm is silenced if the key is turned to ACC.
If both lights and ACC are on, there is +12vdc to both sides of the buzzer. (Buzzer silent.)
If lights are off but ACC is on, the polarity on the buzzer is reversed. (Buzzer silent.)
If both are off, there is ground on both sides of the buzzer. (Buzzer silent.)
But if the lights are on and the ACC is off, there is +12VDC on the 'buzzer +' and ground (through the accessories) on the 'buzzer -'. Current flows through the buzzer and you are reminded to turn off the lights.
Diode is only necessary if the buzzer is not polarized, or if reversing the current on the buzzer might damage it.

[EightBySix]

Would be good to have a separate forum to collect useful electronics help such as this....

Just saying....

[BadMouth]

Would be good to have a separate forum to collect useful electronics help such as this....

Just saying....

This is the right place.  The name of the forum was changed to Automated Projects, which is a little better description.
It still shows up as mrotate in the list as far as I can see though.   

[DaOld Man]

Combination lock to open a 2 door garage.

[DaOld Man]

Very handy and simple timer circuit, using a 555 timer and 4 more parts.
I am incorporating this into my serial port drive, to ignore the flashing outputs until PC has had time to boot up.
Im using 5 volts for the supply, but I think it can go up to 17 volts. (Check specs on your timer to find out for sure.
The electrolytic capacitor will have to be selected by voltage too, good rule of thumb is at least 1.5 times the supply voltage.
I used a 220 uf 10 VDC elec. capacitor.
For Ra I used a 47K resistor in series with a 500K pot, so I could adjust the time. Time range is around 16 seconds to a little over 2 minutes.)
I will post the complete drive circuit when I am finished with it.
How it works:
When power is applied, pin 3 is low, or connected to ground.
The capacitor (C) charges through Ra. When voltage on pins 2 and 6 reach 2/3 of power voltage, pin 3 goes HIGH (+)
When power is removed, the capacitor discharges through the 1N4148 diode. (Quicker reset than it would be if it only had Ra to discharge through.) And pin 3 goes low.

I sent the guy that owns the website an email asking him for permission to use this, but email was returned as un deliverable.
If anyone objects to me using this, please let me know and I will remove it ASAP.
Here is a link to the site, it also has a handy calculator that allows you to choose the proper values for C and Ra, based on the time delay you need.

http://clarkson63.uk/555-timer/operation/frames3.html

[wemr97dl]

Got a question about RGB STRIPs
I want to control RGB Strips with a PAC64LED, looking online I found circuits on running them with Mosfets from an Arduino, not knowing anything about them I thought that these would work
http://www.ebay.com/itm/191850144579?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
here's the data sheet
 http://www.futurlec.com/Transistors/IRL540N.shtml
I put together the circuit but it doesn't turn on from the PAC64LED, using the default script, I know the brightness goes up and down so its probably not getting the full voltage
but if its not switching how will the RGB Color mixing work or fading??
Here's the circuit I was following, any help would be great

[DaOld Man]

Hello wemr97dl!
Sorry for the late reply, but I havent been around here for awhile.
Im not sure what is wrong with your circuit, looks like you have it wired right according to the data sheet.
I'm not real familiar with the arduino so I probably am not qualified to help. However, the only possible problem I can see is you are powering the leds from the arduino  power, could this not be hefty enough current wise?
perhaps try another 12 vdc power supply for the leds, of course you will have to connect the ground from the arduino to the extra PS ground.

[wemr97dl]

Sorry I wasn't more spacific I am powering the led strips from another source, and the ground is common but I'm not using an arduino I'm using a pac64led from ultimarc i don't know if it puts out enough power to turn on the mosfets , the circuit I posted was the example I used.

[DaOld Man]

I was thinking the same thing about the mosfet gate current may be too high.
You might try switching the gate with a small npn transistor. (Ex: 2n222)
Also, those mosfets are good for 26-36 amps. Do you really need something that big?
The pacled puts out 5 volts I think, maybe the voltage is too small for the mosfet gate? The smaller npn would also take care of that.

[wemr97dl]

Would a transistor switch fast enough for PWM FOR THE RGB COLORs

[DaOld Man]

Probably should, depends on the transistor's switching time.

[wemr97dl]

I contacted Andy at ultimarc about Mosfets and he sent me a print of his trackball lighting kit, he used p-channel and i bought n channel, I just need something big enough to handle 39 RGB leds at 12 v, which would be 13 per channel, he used BSH201: P-channel vertical D-MOS logic level FET, what specs would i need to look at when picking one out??

[DaOld Man]

I contacted Andy at ultimarc about Mosfets and he sent me a print of his trackball lighting kit, he used p-channel and i bought n channel, I just need something big enough to handle 39 RGB leds at 12 v, which would be 13 per channel, he used BSH201: P-channel vertical D-MOS logic level FET, what specs would i need to look at when picking one out??

Sorry about the late reply man, I really need to start showing up here more often. (Life, leave me be!)
I would follow andys advice, he knows what he speaks of. (I forgot those cards put out a negative signal to turn on the load. )
Hows this project coming along?

[wemr97dl]

Waiting on mosfets right now for the RGB Strips, but leaving for Vacation in a few days so I wont get back to it for a few weeks.

Here's a link to my project.
http://forum.arcadecontrols.com/index.php/topic,144775.0.html#lastPost


All that is left cabinet wise is Some button inserts for the start buttons and the Plexi for the monitor.
Got to get the RGBs running and start playing with LEDblinky and CPwiz for the second monitor, almost there

[DaOld Man]

Using an opto isolator as an SCR.
SCR (Silicon Controlled Rectifier, a device which conducts a high current when a smaller current is applied to its gate.  The current continues to flow until it is removed, regardless of gate current.  Like a Latch)

I have a small project Im working on and I need an scr.
Radio shack doesnt have it and from the web I have to pay more for the shipping than I do for the part.
So I was thinking, surely I can substitute a part I already have in my junk box?
Well, the old reliable opto isolator came to mind.
On the test breadboard, I used a now obsolete TIL 119 but I dont see why any opto isolator wouldnt work.

What I needed to do was to turn on an led and keep it turned on until I pressed a reset button. I will do a build thread on what Im doing later.
Anyway, the way Im testing the TIL 199 is like this. (See attached diagram).
Pin 1, the anode of the internal led on the 199 connects to the emitter (pin 4) on that same chip through a 460 ohm resistor.
The cathode (pin 2) connects to ground.
The collector (pin 5) connects to + 5VDC.
The load Im will be using is an led with its matching resistor (not shown), which will connect to ground and pin 4. (the emitter)
The trigger that fires this baby also connects to pin 4 and a positive going current is needed.
How it works:
When pin 4 goes high through the trigger,  current flows through the resistor and the chip's led, illuminating the led.
The led, when it lights, forward biases the chips transistor, which allows current to flow to pin 4, keeping the output high and the chip's led on after the trigger source is removed.
The output stays on until the pins 1 and 2 are shorted, or pin 2 is removed from ground. Either of these conditions will turn off the led and reset the circuit.
I found that the circuit powers up when power is applied, I dont know why, maybe a surge starts the transistor to conduct?
So I added the capacitor across pins 1 and 2 to short out the led for a very short time on power up. The short time is determined by how long the capacitor takes to charge.
A smaller value would probably work but thats what I had on hand.

Drawbacks of using this:
Output current is limited to what the Opto Isolator can handle.
Trigger source has to be able to supply output current level.
Trigger source cant go back to ground after going high (might could add a blocking diode if you really need to?)
Also this draws more current than an SCR would, due to the chips LED.
And it takes more parts to do what a small scr alone would do.

I know I can do the same with an OR gate, but I couldnt find one in my junk box.

So i will probably wind up ordering the scrs and paying the high shipping, but I thought some of you guys might find this interesting.

Anyway, hope you enjoy and feel free to add your comments.

[DaOld Man]

I didnt want to post this on the Project Announcements section because it is not arcade related.
This section doesnt get used much so I thought it might be a good place to post it.
Project history:
Years ago, I ran a wire (2 actually) out to a microswitch mounted on my mailbox. Open the mailbox door, switch would close.
Inside the house, the closing of the switch would sound a buzzer for a few seconds then turn on a lamp, which latched by a relay and stayed on until you press
the reset button. You got mail!
This was very handy way back then but after a year or two the wire started deteriorating and the circuit began to fail.
Fast forward to about 3 or 4 years ago from now.
I bought one of those wireless drive way alert things at Harbor Freight (around 13 US bucks).
It had a transmitter with a motion detector that you would mount to detect cars coming into your drive way.
When it detected movement, it would send a signal to the receiver. The receiver would make a rather annoying tone and flash three LEDS on the receiver front.
This was great until it rained, snowed, or an insect would set the thing off in the middle of the night.
After a while it got so annoying I just turned off the receiver.
Fast forward to today:
I was bored and weather sucks so i thought I needed something to do.
I noticed the transmitter was still fastened to the telephone pole in my front yard.
I took it off the pole, brought it in the house, took it apart and cleaned out several years of crud (2 spiders did not fare well that day).
Changed out the 9 V transistor battery, dug out the receiver, dusted it off, changed out the C cell batteries, turned it on to my amazement it still worked.
Hmmm, thought I, maybe this has possibilities.
I put the transmitter in my mailbox and tested it. It didnt work. My mailbox is metal so I figured the metal was blocking the signal.
So i brought the transmitter back in the house. I dropped it and broke a chunk out of the Fresnel lens, but it still worked.
I took the transmitter apart and drilled a hole in the back. I then hot glued a plastic PC board standoff in the hole, ran the antenna wire (about a 6" long wire that was coiled up inside the transmitter), through the plastic standoff. I then glued a rare earth magnet holder to the back of the transmitter.
I drilled a hole in the back of the mailbox big enough for the standoff to go through.
Fed the antenna wire and the standoff through the hole and the magnet firmly held the transmitter in an upright position to the inside back of the mailbox.
It worked like a charm!
Open mailbox, annoying sound goes off in house. You got mail.
That was all good but the system was still missing something. I needed a light to latch on in case I missed it when the alarm went off.
So i took the receiver apart and added an scr in the center led. I also added a Normally Closed button mounted to the top to reset the light when I see that I do have mail.

It works real well, and the mailbox shields from false alarms from wind, rain, snow, whatever.

Well pictures are worth a thousand words and since I already have a thousand words, lets continually with pics!

First here is the transmitter, showing the antenna coming out the back and the magnet holder (the magnet stayed stuck to the back of the mailbox when I pulled this out for the pic.)


Here is the transmitter stuck to the inside back of the box:


And the antenna coming through the back of the mailbox:


Here is the receiver board removed from the enclosure. I marked the jumpers that are used to set the channel. The transmitter has the same jumper layout, so you can have more
than one of these pairs just by setting the channel jumpers differently on both transmitter and receiver. They both must match the same pattern:


And here is the rest switch mounted on the receivers enclosure. I got it a little off center but I can live with it.


Another pic of the switch, showing the two wires I soldered to the switch. The white wire is the antenna, I tried to route it the same way as it originally was.


Switch mounted and circuit board put back in place. i ran the switch wires out so i can get to them. Notice the 3 C cell battery compartment.


I then soldered a 330 ohm resistor in one of the wires going to the reset switch, and the other end of the resistor to the POS (+) terminal on the battery compartment.


I then cut the POS side of the LED center wire and soldered an SCR into it. (Will attach schematic in a few).
The gate of the SCR soldered to the wire going into the board (was LED lead).
The cathode of the SCR soldered to the lead going to the LED.
The Anode of the SCR solders to the other wire of the reset switch.


Put enclosure halves back together,  installed C cells and tested. Works like a charm!

Here is the receiver, standing by patiently for a new signal from the transmitter.


I walked out to the mailbox and opened the door, came back in and this is what I saw:


It's saying, "hey stupid, you got mail!"
Press of the button turns off the led.
The noise maker and the leds flash when you power this up, so I couldnt use the on.off switch as a rest. Bummer.

And here is the quickly drawn schematic:



I ordered ten of those SCRs from bgmicro.com:

[DaOld Man]

I splurged and bought another one of those drive way alert thinggys.
I had a Harbor Freight 20% off coupon and it was burning a hole in my pocket.
After getting home and tearing it apart I was disappointed.
They have changed the circuit boards.
Here is the transmitter with back removed:


Here is the transmitter board removed:


First thing I noticed was it looks cheaper made than the old one I had.
Also, for the antenna it has a coiled spring, not the wire I was expecting.
This wont matter if your mailbox is plastic, but is its metal, the signal wont get through.
I suppose the spring could be de-soldered and a piece of wire soldered back, so the antenna could exit out of the back of the metal mail box, like I did the first time.
But I have no idea if this will mess with the tuning. Maybe some of you guys with radio experience can tell me.
Also, they are using a different chip now, and this one as far as I can tell is not addressable, looks like from info I found on the web, channel is set by capacitors, and they are tiny SMD capacitors,
so changing the channel on these new ones is going to be nearly impossible, however it shouldnt be a problem as long as your neighbor is not using one on the same channel.
The chip in the transmitter is EG0001 if you want to do some research.

Now the bad news.
Here is the receiver with the back removed:


And here the board removed:


The big problem is that these leds are wired with the anodes wired together (positive is common).
That means the chip that turns on the LED outputs a negative to the LED, and not a positive like my first one did.
This is going to make it hard to wire in the SCR like I did before, to latch the LED on.
SCR needs a positive trigger on the gate to fire it.
back to the drawing board I guess.

One thing I do like about this new model, it only has one switch, off/hi/low whereas the other had two, on/off and hi/low.
Thats about all I like about it.
The LEDs still fire for a second on power on so I cant use it to reset the LED. which means I will still need a pushbutton for reset.

[DaOld Man]

Well, I wound up the first latch circuit I discussed before getting on this latest trip.
I used an Opto Isolator to latch on the LED.
I had to wire it a little different from my first example, since it had to take a negative pulse to latch on.
Here is a schematic:

A negative pulse from the circuit board fires the opto isolators LED and the receivers LED, through the two 330 ohm resistors, and the on board LED which I have no idea what its value is.
Once the opto isolators LED is on, the transistor conducts, keeping both LEDs on.
This circuit draws at least twice the current that the SCR circuit did, due to both LEDs being on (opto isolator and receiver).
I dont know how this will work when the batteries get weak, the 3 resistors may cut voltage enough to not turn on the opto isolator LED.
But for now it is working.

Here is my Opto Isolator with two resistors soldered to the pins. I am getting the signal trigger off one of the on board LED leads. Im getting the +VCC from the other LED. The + wire (red) goes to the reset button then back to the opto isolator (white wire). The blue wire goes to battery pack, neg terminal.


After testing, I hot glued it to the circuit board to keep everything stable and fastened down.
Got a little sloppy but more is better, right?
I added a piece of heat shrink to cover where the blue ground wire connects to the opto-isolator lead.


And here it is all finished. Board fastened to housing. Reset button mounted and white and red wires soldered to it. Blue wire soldered to the negative terminal on the battery pack.


And that is that. If I use this setup on a metal mail box I will have to come up with a way to get the antenna outside the box.
I may play around with replacing the spring antenna with a piece of wire.
Note to self: the scr method is a lot easier, wish they made a scr that triggers off a negative pulse, but Ive never seen one.

[PL1]

Got a little sloppy but more is better, right?

As the old saying goes, "The bigger the blob, the better the job!"     jk


Scott

[DaOld Man]

Then I should be the best LOL.
You know this could be made a lot simpler if I could get into the chip and reprogram it, but I have no idea how they do it, the numbers on most of the chips are rubbed off, so not even sure what they are.
There is no programming port so you would have to do some fancy soldering.

[DaOld Man]

I found another version of the drive way alerter at Harbour Freight.
This one had a sticker that said "channel 1" on it so I figured it was the same as the first one I converted. And with coupon it was a little over 9 bucks so I thought "what the heck".
I took it apart and it is yet another version of the board. (Sorry no pics).
It does use the same chip as the first one in the transmitter, but the address jumpers are surface mount pads that you have to bridge with solder to set.
Also this one is only using 4 of the possible combinations to address it. It uses the same chip, so you could still address it on the unused pins of the chip, but you'd have to do some fancy soldering.
The receiver end is different too. It uses surface mounted LEDs, but the good news is that they use ground for common, so the SCR I have works.
Just have to cut back some of the trace to the LED and solder the scr in to it.
EXCEPT: The scr would not stay latched on. I first thought i had a bad scr or damaged that one with solder iron heat, so I swapped it out, but only to have same results.
After some trouble shooting, I found they used a different LED driver chip on this version. When the output of the chip goes high, it turns on the LED, but when the chip commands the led to turn off , instead of floating like the first version did, it goes to ground. This effectively turns off the scr, hence scr not latching on.
I fixed this by adding a diode in the gate circuit, to block a negative (low) signal from the scr.
It works, but this is 3 different versions of the same device, so who knows what they will come up with next?