Tech Forum Questions

Yes, you can wire parts together in free air following the schematic and in most cases it will work just fine. Indeed I have done just this on a few occasions, either to lash up a very simple circuit to test or for artistic reasons. In general though I would recommend other techniques for day to day use. Do some searching online for electronic prototyping and building techniques, there are countless methods that have been developed over the years and you are sure to find something suitable.

Perfboard is a good simple one that I've used many times. I would also recommend becoming proficient at reading schematics and identifying components prior to jumping in. It will save you much time and headaches in the long run.

There are plenty of examples of building circuits without a PC board available on the net. http://blog.makezine.com/tag/freeform/ is an excellent example of this type of freeform circuit building. It is sometimes a little more complicated than using a printed circuit board pattern, but for some circuits, it's more practical. As long as no leads touch were they shouldn't, and as long as stray capacitance isn't an issue, the circuits will function just fine.

Whether you can simply connect components as shown in the schematic without regard to parts layout and lead dress depends entirely on the project.

For "DC" projects, such as a demonstration of an AND gate with two switches, an LED, perhaps an IC, a few resistors, and maybe a bypass capacitor, parts layout isn't critical so long as the bypass capacitor (from Vcc to ground) is physically close to the IC. It would even be OK to solder component leads together with no substructure or framework.

On the other hand, for radio frequency work (FM receivers, AM receivers, garage door openers, etc.), and for any project with a microprocessor, parts layout is critical, and you should follow the perfboard layout or printed circuit layout published with the schematic. If you don't, stray inductance and capacitance can wreak havoc with the circuit, and unwanted oscillation may even occur.

In between are audio frequency projects. For high-impedance projects, generally those with a low-level signal input, layout is critical.

However, for low-impedance projects, such as a circuit to drive a speaker from the output of an MP3 player, layout isn't critical.

The biggest issue with what you would like to do is that typical CCD sensors are a fraction the size of a 35mm film frame. In order for the existing optics to focus properly onto the sensor, it has to be located in the same plane the film would be. If you install a 1/3 inch CCD in a 35mm film camera, you will only be capturing a small portion of the field of view. Anything is possible with enough effort, but given the low price of some very good digital cameras these days, you are better off buying one than trying to convert something and ending up with inferior results.

When you look across either sensor you will see negative going pulses. When the beam is broken it changes to supply voltage, no pulses. If you would like a schematic to "hack" this information send me a request. It is essentially a missing pulse detector.

All openers are not the same, but most are similar. You want to see when the beam is obstructed when the door is open, but you really only need to know when the beam is broken because if the door is closed, nothing can enter to break the beam. You can install an end of door travel switch in series with the relay if you like. With the beam intact, a scope shows pulses going toward ground but not to ground. A broken beam stops pulses and voltage remains at maximum.

When you look across either sensor you will see negative going pulses. When the beam is broken it changes to supply voltage, no pulses.

I used a LM555 because it contains differential amps to monitor voltage levels and will source or sink to 200ma. If your pulses go down to 1/3 of supply.. circuit with diode input will work ... if not, use transistor input. Any general xsistor, such as a 2N2222, will work. I'll stop here, but feel free to ask questions!

This will vary from one garage door opener to another, but most that I've seen have an LED either on the photo beam receiver or on the opener itself that illuminates when the beam is intact. If I wanted a relay to trigger, I would tap into this LED. If you want to interface to it without modifying anything, a phototransistor or CdS cell could be mounted over it to detect light from the LED. Anything else will require some reverse engineering on your particular opener.

The two solutions above are good but I think they are both overly complex. I assume that the reason for the time delay is that the wireless system produces a pulse whose duration is too short to properly trigger (and latch) the garage door relay. I know that my garage door will stop if the button push is of too short a duration. So we need to stretch the signal from the wireless system and we probably need to make the voltage of the wireless system compatible with the 24V relay in the garage door opener.

Looking back a couple months in Nuts & Volts there is an article about a circuit that turns on a laser to help park a car at the proper place in a garage. The circuit uses the sound of the garage door opener's operation to turn on the lasers for a minute or so. The article is Nuts and Volts - May 2012 - Page 40 - "Build a sound-activated laser parking system." I think the second op-amp stage from that circuit might be all that you need.

The op-amp is setup as a comparator with the reference voltage level set by Potentiometer P1. The other input is from an amplifier stage but I think you could just directly couple the wireless device to that op-amp input (perhaps via a largish value resistor to give some isolation). You would set P1 so that the reference voltage is a bit less than whatever the wireless system puts out.

When the wireless signal is high the comparator swings to the voltage rail charging cap C2. When the wireless signal goes away the op-amp goes off but C2 is kept from discharging back through the op-amp by diode D1. The voltage on the cap turns on the mosfet T1 which you can use to control the current to the relay's coil (replace the laser diodes with the relay's coil in the circuit). The combination of R5 and C2 controls how long the mosfet is turned on.

In the publication the author was going for a couple minutes. If you only want a couple seconds then R5 and C2 can both be made smaller to decrease the on time. As a rough estimate the on time is about 2/(R5*C2) seconds. So R5=1M and C5=1uF should give an on time of about 2 seconds.

I assume that the need is to have a delay before opening or closing the garage door. The circuit diagram below will do this.
 

The circuit shown here, uses a 1Hz oscillator (ICL555) which clocks a 4015 shift register as a sequencer. When the output of pin 2 goes high, the 4N35 optocoupler conducts. The output shorts across a garage door pushbutton.
 

The "Desa Int’l wireless doorbell" will need to close the switch shown as "Enable PB." This can be done with either another optocoupler or suitable transistor logic to simulate the switch closure. In operation, the Enable signal (pin 15) must be active high long enough to be captured on the next clock edge. When the yellow LED goes on, the input has been captured. For the circuit shown, the delay is about four seconds. Increase the clock frequency by decreasing the 560K and/or 330K resistors in the clock section.
 

Note the series wiring of the RLED resistor, optocoupler (LED), and red LED. The 47 ohm resistor must be changed if the circuit is to operate on higher voltages, up to the 15 volt limit of CMOS. Use Ohm's Law to get 20 mA of current through the optocoupler / RLED combo. For the RLED value shown (47 ohm), a six volt supply is required. In practice, I took the circuit board from a cell phone car adapter and "floated" it with a diode to get the six volt regulated output. From a 24 volt source, I use a 12 volt series zener to drop the voltage to 12 volts to the cell phone car adapter. A one watt zener is sufficient.
 

Originally, I tried using a CD4060 for this, but found the circuit to be more predictable. The approximate component placement is shown below the circuit. Actual wiring may vary! The circuit has been in operation for over six months now and works great. If an actual pushbutton is used, the circuit may have potential electrostatic discharge susceptibility through the pushbutton to the D input. While I have not had issues with this, I have a small grounded loop near the pushbutton to reduce static discharge through it. Using a pushbutton with a grounded static shield is recommended.
 

Most parts (including the solderable breadboard) are from AllElectonics.com, though the 4015 is from Digi-Key.

This sounds like a classic application for the ubiquitous 555 timer IC.

The datasheet for the 555 includes many examples of using it, including the one-shot circuit that I think will meet your needs nicely. You can use a common transistor like the 2N2222 to drive the relay coil. Don't forget to put a reversed diode across the relay coil to protect the transistor.

The first place I saw the oscilloscope multipath display was on the Marantz 10b. Two other FM tuners with the scope outputs were the Scott 312 (and the Scott 312b, plus the kit versions LT112 and LT-112b) and the Heathkit AJ-15 (and the receiver version AR-15). You need an X-Y oscilloscope — preferably with response down to DC. Connect the horizontal X input to the output from the audio detector (still monophonic, not yet demultiplexed) and connect the vertical Y input to the AGC (automatic gain control) signal.

Check out the Oersted Technology article at http://oersted.com/magnetizing.PDF.

I'm reading between the lines here,  so I apologize up front if I'm in the wrong universe with my answer.

I see 2 main approaches (off the top of my head) - build an LED illumination thingy from scratch, or buy LED spotlight bulbs 'off the shelf' and fabricate whatever you need to get enough light.

Get It Off The Shelf
A fairly long search on google found all sorts of possibilities, if you only want to get some E26 base bulbs and create an array of <n> LED spotlight bulbs to supply he desired light level. If you assume your 200W incandescent bulb puts out something in the neighborhood of 3000 lumens, then you need about 7 or 8 420-lumen spots like the Grainger 3CRA2 (Optiled model 1503050217) - which Grainger sells for $45 each… Or just 3 of the 6XWKD (GE Lighting LED20P38S830/25) which puts out 1050 lumens (at $60 each) would also supply the desired light output.

If you want to go this way, google is probably your best friend. (Along with eBay). Use "LED spotlight" or "LED high-power" or "LED 20W" (or even "LED e26", which is what I started with).

Build It Yourself
Googling for 20W LEDs, I found www.hero-ledstore.com/heroled-20w-led-c-2_184.html with all the parts you'd need to make a 20W LED lamp (but that's gonna run you about $74 and you still need 2 of them (apparently they are 1600 lumens each). Interestingly, the parts to make a 50W (4000 lumen) 'system' are only about $175 - and you'd only need one of those… There are other options out there also, I'm sure, as a google for "high power LED" returned about 78 million hits "wink." The thing there is that you need a constant-current source to feed the LEDs with, not a constant voltage (but with voltage limits, IIRC).

Look here www.pjrc.com/teensy/td_libs_DogLcd.html