Tech Forum Questions

Try Elenco WK-106 Hook Up Wire kits which has 6 colors (red, yellow, black, white, green, blue) of 22 gauge wire in 25 foot rolls for around $15. See the web site Elenco WK106 Hook-Up Wire Kit 6 Colors.

I am going to try to answer your question from the standpoint of a person solving your problem on a contractual basis, and who, therefore, must deliver the best design at the lowest cost. I think that this is the most objective, efficient way to approach the problem and to give you a reasonable answer.

With all due respect, you have left out important — or included ambiguous — information needed in order to arrive at a design which meets your exact needs.

For example, you have not specified any type of physical form factor. Do you want to replace a single 300-watt incandescent bulb, or an array of bulbs emitting 5900 lumens? What do you mean by “fool the human eye into thinking it is seeing a brighter, more pleasant level of lumens.”

Regarding the latter:

White LEDs come in a minimum of two different colors — warm white (color temp. approx 2800K; simulates incandescent output), and cool, or bright, white (color temp. approx. 6000K; just about simulates daylight and fluorescent lighting). These LEDs are very commonplace, being available from, among other sources, www.superbrightleds.com, Amazon, and others. Just make certain you buy from a reputable source which will stand behind its product.

One could certainly design and build for you a light (lights?) meeting your specific requirements, using readily-available 100-watt LEDs (warm white or cool white), along with the appropriate power supply AND — most importantly — cooling. VERY SERIOUS cooling.

As the situation stands currently, my suggestion to you is the following: LED technology, and the LED lighting industry is very mature; so much so that there is no need for an individual, or firm, to waste his or its valuable time designing a high-power LED lamp or lighting fixture which has

  (a) most likely already been designed, or

  (b) which can be easily adapted to the user’s specifications from an existing design of a reputable LED lighting manufacturer (you may be surprised to know that, as of this moment, LED “drop-in” replacement lamps are available to replace standard fluorescent tubes, while providing the very much longer life and very low power requirement of LEDs).

If I were you, I’d start by putting out feelers to companies such as www.superbrightleds.com, who have already designed, and offer for sale all types of lighting solutions.

I realize, as a tinkerer, hacker, and design engineer myself, who loves nothing more than to make something useful out of a pile of components, that this solution is somewhat distasteful.

You CAN design a solution yourself, if the situation warrants. You CAN do it. BUT... if you’re attempting this for reasons other than self-satisfaction, then save yourself time and money, and go with the solution which the experts most probably already have.

By the way, just in case the fact escapes you — Due to the semiconductor physics involved, LEDs at the output level you need do not provide any significant power savings over incandescent technology, or other lighting technologies, for that matter. Three LEDs capable of a total output in the range of 5500 to 6000 lumens will require power of approximately 100 watts each. Total = 300 watts (not including active cooling), the same as the incandescent you want to replace. If you’re thinking that the much longer life of SMALL semiconductor LEDs justifies the transition, you should know that the jury is still out on just how seriously the lifetime of high-powered LEDs is affected by the heat that is generated by the current required for all this super-brightness. Some of the jury think it’s end-game, for now, until there’s a major breakthrough in LED technology.

I recently replaced twelve 300-watt incandescent lamps with LED floods. In my case, it was made easier because the 300-watt lamps illuminated hanging lamp enclosures in a church. The overall purpose was to provide reading illumination for the congregants.

If this application suits your purpose, look at Lighting Science DFN38WWV2NFL120, being a 120V 24-watt PAR38 lamp, 3000K. These lamps, while only rated at 1300 lumens, put all of their light output in one direction —downwards — while the incandescent lamps spread their 5900 lumens all over the room. And they’re dimmable. It was a no-brainer for us because they worked in the application and the electrical demand for the lighting went from 3600 watts to 288 watts.

One on-line source is https://www.1000bulbs.com/product/63140/LED-PAR38242530.html, but your local electrical supply jobber might get you a better price — especially if your state is currently giving rebates for so-called “green” appliances.

If you etch copper off a copper-clad PCB, you sure don't want to port etchant into copper pipes! And you don't want the copper ions from the etched board going into the waste-water system. After all, we all live downstream of someone else. MG Chemicals offers two disposal ideas, which you can read here. www.mgchemicals.com/tech-support/ferric_faq/.

Their is also a whole house surge-protector from Square D and other electrical panel suppliers for less than $150. They hook up to both sides of the 220 volt buss bars. Check you panels maker site. I purchased one a number of years ago and it stopped electrical line spikes. With a cable and phone line surge-bar I have been lucky and keeping my replacement money in the bank.

The simplest solution to lightning-induced surge protection is to use a commercially available surge-protected outlet strip. There are numerous sources for these items, and you may even find a suitable device at your local hardware store.

The important thing to understand is that a lightning strike conducts huge oscillatory currents. A varying electrical current will generate a changing magnetic field, which in turn will induce superimposed voltages in nearby conductors -- including service drops from the utility pole to your house (e.g., electrical power, TV/internet cable, and telephone). Such surges can be induced both line-to-line and line-to-ground in the electrical power service drop (and for balanced-line applications such as telephone). Properly-designed surge suppressors provide both line-to-ground and line-to-line protection for such circuits.

Surge voltages induced line-to-ground arise because such devices often are connected to more than one source of surge voltage: For example, your television set is connected to utility power and also connected to the TV signal cable. Likewise, your computer may be connected to utility power, to a cable from your internet service provider, and to a telephone cable (for fax service).  Unless these cables/wires are all run together throughout the house (and this practice is discouraged due to the possibility of capacitive cross-coupling), one or more loops exist, and within each loop, the surge voltage induced by the lightning strike is a direct function of the areas enclosed by the loop.

It follows that effective surge suppression can only be accomplished by feeding all of the incoming electrical services through what is called a "surge-protective window". In such a structure, surge suppression elements such as metal oxide varistors (MOVs), avalanche diodes, or gas tubes can clamp impulse voltages to a common reference point plane which in turn is connected to earth ground. This can be effected by using a surge-protected outlet strip that also incorporates protection for telephone and cable lines. Typical examples of this all-inclusive surge protection are devices available from Belkin (e.g., www.belkin.com/us/BV112234-08-Belkin/p/P-BV112234-08/) and Tripp-Lite (e.g., www.tripplite.com/av-home-theater-surge-protector-isobar-10-outlets-8-ft-cord-3240-joule-3-line-coax-ethernet-tel-network~AVBAR10/).

All cables exiting the surge suppressor block should be run together wherever possible, secured periodically by twist-ties or other means.  This method ensures that negligible induction areas exist into which surge voltages can be introduced. Capacitive-coupled interactions are no longer a problem because any prior surge voltages have already been stripped from the cables by the surge suppressor block.

Please note that the protectors identified above are "Cadillacs" because they provide surge suppression for all common power and media transport wiring. Sometimes just a simple one-outlet surge suppressor will do the job — or, for example, a single-outlet suppressor with built-in telephone line surge suppression, both at significantly lower cost. I even use single-outlet surge suppressors to protect my coffee maker and washing machine because each of these devices contains electronic modules that are expensive to repair.

The important consideration is to maintain the "surge protective window" approach to the problem as outlined above.

Lightning protection is a complex issue, including home entrance cable protection, bonding of large metallic structures, and even grounding of rain gutters and downspouts. A good place to start is a free PDF from www.lightningsafety.com/nlsi_lhm/IEEE_Guide.pdf. Because a lightning bolt can pack a 500 MJ wallop, far beyond any MOV rating, surge protectors are not protection against a direct strike, but they do help limit inductive surges (e.g. lightning hitting a tree nearby, inducing a current in house wiring). In brief, running a hefty ground wire from gutters, external antennas etc. to an effective ground in conductive soil is the first line of defense.

MOV surge suppressors have saved my PC and appliances from one damaging surge, though, as shown by blown internal fuses and smoking MOV's!

The CP-290 is very old and was sold in the early 1980s. The communication protocol is RS232 serial

Baud Rate:  600
Data Bits: 8
Parity: None
Stop Bits: 1

The connector on the back is a standard 5-Pin DIN socket. Looking at the back of the unit the pins are 5-4-3-2-1 starting at the left and going counter-clockwise to the right with pin 5 on the left, 3 on the bottom and 1 on the right.

Pin 1 - No Connection
Pin 2 - Receive Data (In)
Pin 3 - Ground
Pin 4 - Transmit Data (Out)
Pin 5 - No Connection

To plug into a computer like an IBM compatible these connections would go to a 9-Pin female serial connector:

CP290 —> DE9
2 RxD —> 3 Txd
3 Gnd —> 5 Gnd
4 TxD —> 2 RxD

Attached is a scanned image from the manual.

The 5-pin DIN (pins 1-5) — The middle pin (3) is GND, the pins on either side (2 & 4) are Rx & Tx. I don't recall which. You might have to swap them to work. The outer pins are not connected.

From the CP290 programming guide:

Pin 1 - No Connection
Pin 2 - Receive (input)
Pin 3 - Ground
Pin 4 - Transmit (output)
Pin 5 - No connection

Looking at the face of the connector with Pin 1 at the 3 o'clock position and Pin 5 at the 9 o'clock position.

I could give you a lot of technobabble, but the truth is there's no practical difference between 1N34A and 1N60 in this application. Most people get a bag of diodes, preferably from different batches, and check them for the loudest signal with best sound quality.

Both diodes — 1N34 and 1N60 —­ are germanium diodes, and both are of similar physical size. The important thing is that this diode family has the smallest forward voltage characteristic, which is important for rectification of small voltages. They both will operate at radio frequencies. The forward current rating and the reverse voltage characteristics are unimportant in this application.

Bottom line: Either one will work in this application. My personal choice would be the 1N60 because the documentation available for this device is superior, with V-I curves to show the typical forward voltage characteristic.

Either should work well. Both have a conduction knee starting around 0.15 or 0.20 volts. The IN60, being slightly newer, probably has more tightly-controlled specs. One source for diodes and their specifications: http://store.americanmicrosemiconductor.com/1n60.html and http://store.americanmicrosemiconductor.com/1n34a.html. BTW, for better Q of the tuner, connect the diode to a tap on the coil.

You can use either type and expect the same results. Both diodes are germanium and both have a forward voltage drop, (often called “turn-on” voltage — where a diode begins conducting), of about 0.3V. A diode with even lower forward voltage is the 1N5817, a Schottky diode, which has a forward voltage of about 0.16 volts. The forward voltage determines how weak a signal can be heard.

The author at the following URL presents a comprehensive table of 1N34 and 1N60 subtypes and a few Schottky diodes used as detectors in crystal radios. If you view it, look in the column labelled Measured Vr. http://wiki.waggy.org/dokuwiki/crystal_radio/detector. However, long before the sensitivity of the diode becomes the limiting factor, four other factors will limit the performance of the radio you propose. Those are:
   Selectivity — only one tuned circuit is used and it is not impedance matched at input or output.
   Antenna length — definitely use more than 10 feet — a goal would be 50 feet and as high as possible.
   Ground losses — connect a wire to Earth or to a large expanse of metal.
   Frequency of operation (also related to selectivity) — with this type of circuit, as you increase frequency, the bandwidth increases. This means it lets through more and more stations at the same time.

If you haven’t had the opportunity to read them, you’ll probably find the insights in the wiki entry on crystal radios time saving. Especially note the sections on tuned circuits, impedance matching, and the problem of selectivity. It can be found at: http://en.wikipedia.org/wiki/Crystal_radio The following URL shows how to connect your tuning circuit and diode directly to your LM386 without the LM741 you have in the middle of the circuit. http://makerf.com/posts/an_lm386_powered_crystal_radio_in_an_altoids_smalls_tin

You specified a number of turns for your coil but I didn’t see any diameter for the it. Starting coil designs would be 56 turns for a 5 inch diameter oatmeal box or 75 turns on a 2 1/8 inch diameter coil, each of which could be used with your 365 pf variable capacitor. 22 to 24 AWG bare enameled wire would work for the 5" diameter. 28 to 30 AWG would work for the 2 1/8" diameter.

To help optimize selectivity, you want what's called a "square coil." This means the coil length is about equal to the diameter. Not critical but helpful. Small diameter wire increases resistance which degrades selectivity. It likely to be less frustrating to first get your design working at the lower AM broadcast band frequencies before pushing up into the shortwave frequencies.

Last, it looks like you might put taps on your coil. The following URL has photos that might give you helpful ideas. Once on the website, click on the “Oatmeal box crystal set.” www.midnightscience.com/download%20files/XSOB1-manual-050108.pdf Please accept my apologies if I've included to much information. Best wishes for your success.

The LM4120 regulator only puts out a few mA, and this 1.5V application is at the bottom end of the part's voltage range specs. When connected to clocks that need a bit more juice, the regulator sags and puts noise on the DC supply, and that screws up the time keeping.  Solution: Look for a beefier LDO, ensure the wall wart is putting out clean DC when loaded by the clock, and ensure the LDO's input voltage is sufficiently higher that the 1.5V LDO output.

I recommend looking at the LM4120 output with a DC coupled oscilloscope and checking for noise or voltage drift, either short-term or long-term. I think you will see the problem.

I used battery clocks in an amp hour counter device and found my clocks running slow, sometimes stopping. Maybe your problem is related to mine. It seems that the pulse current to run the ticking solenoid is relatively high. Adding a 100µf electrolytic plus a 1µf ceramic cap directly on my fake battery (wooden dowel with screws on the ends) fixed the problem.

First off, I suggest doing the following:

   1. Measure the OPEN-CIRCUIT output of your eliminator before connecting it to the clock you want to run.
   2. Connect the eliminator to the clock, then measure the voltage output again.

If the difference between the "no-load" voltage and "load" voltage is more than 0.5 VDC, it's entirely possible your wart isn't delivering enough current to properly operate the regulator. In this case, try a similar-voltage wart with higher current output (say, 1.5-2X of your current wart). This may solve the problem as wall wart outputs tend to droop severely once you approach their maximum current capability, resulting in severe output instability, (i.e., the regulator won't "regulate" well), increased ripple, noise on the DC output, and severely shortening the life of the wart (i.e., overheating and such).

If the "no-load/load" voltage difference is negligible (< 0.1 VDC), try adding a filter capacitor, (start with 470 µF electrolytic — watch the voltage rating of the cap!), paralleled with with a 0.01µF mica or polyester to filter out high-frequency hash that may be on the DC output feeding the clock. This may give you the stability you're looking for as most, if not all, warts are half-wave, unregulated types with very minimal filtering to begin with. Adding more filtering (larger electrolytic) and bypass (small value) caps to the DC output greatly improves their overall stability and cleanliness of the DC output voltage.

Finally, (as you already know), having a regulator between the wart and your device guarantees a rock solid DC source, as long as you don't pull too much current from the wart.

Without more information, it's difficult to give a definite answer, but here are three possible causes to check:
  1. Is the output voltage correct? Check with a DVM; anything from 1.35 to 1.6 V should be OK for LCD or quartz clocks.
  2. The power supply has excessive AC in the output, e.g., a bad capacitor. Though you could check this with an audio amplifier or oscilloscope, it's easier to just put a 500 microfarad or larger electrolytic cap across the output and see if that fixes the issue.
  3. AC or RF leakage from the power supply, either from the mains or from a nearby radio transmitter, is making its way into the clock. The clock circuitry is very low power, so any AC could flip some flip-flops a few extra times per second. To check this, you could make a Faraday cage (e.g. window screening) around the clock and connect it to one side of the supply. This is to satisfy your intellectual curiosity, though it's probably not a convenient way to run a clock 😉