Tech Forum Questions

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 😉

By using the resistance and capacitance values for the IC5A 556 timer IC we get one-shot periods between 0.5 and 1.6 seconds for the kHz switch position, and between 0.5 and 1.6 msec in the Hz position. The trimmers would adjust these to 1.00 sec and 1.00 msec respectively. I believe the switch labels (Hz and kHz) in the schematic diagram got swapped. The 1-sec period would let the counters count 0 to 999 pulses (0-1 kHz) and the 1 msec period would open the counters to count from 0 to 999 kHz (0-1 MHz). The calculations eliminate the possibility of IC1 as a prescaler or divide-by-x counter. Thus, IC1 probably is an obsolete CD4583. Don't give up hope: A CMOS Schmitt trigger CD4093 will do the same job, although it requires some rewiring. DigiKey has many in stock for under a dollar.

According to my ancient Motorola CMOS databook, MC14583B is a dual Schmitt trigger in a 16 pin package.  Channels A and B can be used independently or there is an exclusive OR output on pin 14. The outputs are tri-state with the control on pin 13. Pin 13 is not connected which is very, very bad practice. However, channel B input (pin 15) is tied high so only channel A is being used. Therefore, you can use any garden variety Schmitt trigger in its place.

The 4583 IC in your frequency counter is a non inverting dual Schmidt trigger. I found this in an old Motorola CMOS data book from 1991 #Q4/91 DL131 REV 3 on page 6-498. The Motorola part number is actually MC14583B. Only the A Schmidt is used in your circuit, the B Schmidt is unused. The Schmidt trigger is used in front of the counter IC1 to ensure a clean input to the counter. Typically the Schmidt trigger output will transition low when the input drops below 40% of the supply voltage and the output will go high when the input goes above 60% of the supply voltage. For the MC14583B device these thresholds are adjustable via external resistors through the positive, negative and common terminals. In your circuit those three pins 5, 6 and 7 are bussed together without a resistor and this sets the thresholds to around 40% and 60% of the supply voltage.

Pin 9 is the A input
Pin 4 is the A output
Pin 15 is the B input (unused so tied high to 9V)
Pin 10 is the B output (unused)
Pin 5 is the negative A (pins 5,6 & 7 are tied together to set the A device threshold)
Pin 6 is the positive A
Pin 7 is the common A
Pins 1, 2 and 3 are common, positive and negative for the B Schmidt (unused)
Pin 16 is VDD. Supply voltage, 18volt max for this device
Pin 8 is VSS. Supply voltage return.

A replacement for the '4583' could be the MC14093B or CD4093 available from Newark, etc., although these do not have adjustable thresholds they will be close to those of the 4583. These are quad two input NAND Schmidt triggers, so all unused input pins must be tied high (to 9V in your case).

I found an MC14583B IC in a 1991 Motorola Data Book. This part is a dual Schmidt trigger IC and appears to match the pinout  shown in the schematic. The pinout is not fully legible in the electronic issue. Using a Schmidt trigger in this application makes sense. I have attached a photo of the data sheet.

If IC1 is indeed an MC14583B or equivalent it should not be powered from 9V! The logic high output from Q1 is only 5V. The data sheet for the MC14583B indicates the minimum input voltage required to guarantee a logic high to be 80% of it's supply voltage. Also the logic high output voltage from IC1 is too high for the 5V downstream logic.

It is possible that IC1 is not actually defective but is not seeing a logic high due to poor design. This theory can be tested by substituting a 7 volt power supply for the battery. If it works at the lower voltage, I would modify the circuit to power IC1 from 5V.

I also question not having a resistor between the junction R1/C1 and the base of Q1 to limit input current to a non destructive level! This might best be accomplished by cutting a 1/16" gap in the track leading to the base of Q1 and soldering a 1K surface mount resistor across the gap.

Am attaching a ZIP file with 4 scanned pages of the MC14583B data sheet for your information. MC14583B.zip

The answer to question 11151 is it is an NE556 dual timer.

The chip you are looking for is a CMOS 4583. It is a dual adjustable  schmidtt  trigger. The 556 timer clocks the 4583 like a gate. I checked the usual places and it may be obsolete.

The best match for IC1 that I found is a Dual Schmitt Trigger, TC4583BP or NTE4583B.

Because most of the other ICs in this circuit are standard 4000-series CMOS parts, that indicates the 4583 at IC1 likely is also. Using that to refine the search, the part is a dual Schmitt trigger buffer.

The unique property of a Schmitt trigger gate is that it provides hysteresis.  When a slow-rising, slow-falling, or noisy analog signal is applied to an ordinary gate, that gate may oscillate and switch several times as the input crosses its switching threshold. But because this Schmitt trigger requires a much higher input voltage to switch high than it does to switch back low, it will clean up its analog input, and its output will switch only a single time.

In this circuit, that behavior is important because the input signal is being used as a clock for the counters.  Without the Schmitt trigger, some input signals might trigger multiple clock pulses per cycle, resulting in wildly incorrect frequency numbers.

Searching for Motorola's specific version number of this part, MC14583BCP, seems to produce better search results, revealing data sheets and even a seller of the part on Amazon!  However, because the circuit does not actually take advantage of the unique programmable hysteresis feature of the 4583 (by just tying pins 5, 6, and 7 together), any other CMOS Schmitt trigger should work just as well, if you can find something cheaper and don't mind slightly modifying the circuit.

This appears to be a dual Schmitt Trigger. I found the NTE4583B data sheet at: www.nteinc.com/specs/4500to4599/pdf/nte4583B.pdf VCC, GND placement is consistent with your Fig 1 schematic. Pin 9 is "A In" and Pin 4 is "A Out". So this would appear to be a Schmitt Trigger used to clean up the input signal.

The 4583, in that design, is an obsolete dual Schmidt trigger chip, which is intended to square up the input signal so it meets the minimum rise/fall time requirements of the downstream counter chips. Probably the simplest substitution would be a 4584 / 74C14 hex Schmidt trigger chip, with two of its inverters wired in series. The remaining four inverters should have their inputs grounded, to prevent excessive current consumption.

The chip you asked about the CD4583 is what is known as a Dual Schmitt Trigger ... that chip has been discontinued but some stores still have the NTE4583B which was their substitute for it. I have attached a .pdf file of the NTE Data Sheet for this chip. Worst case is you would need to rewire the schematic to use a more current version of an equivalent chip. nte4583B.pdf

One such store that says they have them is listed below:

www.moyerelectronics.com/BVModules/ProductTemplates/MoyerProductTemp/Product.aspx?productid=1e4bffa7-6961-4e1a-82f7-8a161ab401ea

Try looking at a MC14583B dual schmitt triger with only one side used. Pin out looks correct, Pin 9 is input and Pin 4 is output. Pins 5, 6, 7 are used to adjust hysteresis.

The 4583 is this part: www.nteinc.com/specs/4500to4599/pdf/nte4583B.pdf.

According to all my old data books, the 4583 IC is a Dual Schmitt Trigger, and NTE supplied them to the service industry, part number NTE4583. You can look at their data sheet here:
www.nteinc.com/specs/4500to4599/pdf/nte4583B.pdf

Supposedly, a company called "Mountain States Electronics has one in stock. Here is their address and contact info:
2107 South College Avenue
Fort Collins, CO 80526

Since the inventory for Mountain States showed only 1 in stock, here is another supplier of the TC4583 Schmitt Trigger chip. These people have a bunch of them and the price is definitely right:
http://store.americanmicrosemiconductor.com/tc4583bp.html

This is a common problem in any sensors that deal with moisture (soil moisture sensing or rain detectors or water level meters). Stainless steel probes may work better. I had better luck with non-metallic conductive probes. I use carbon rods from old carbon-zinc batteries. Carbon, most of the time does not react the way metals do and when it does, it does not cause non-conductive oxide layer like metals. If you can find conductive carbon rods, (I hope modern battery cells still have carbon rods) please try them out.

If the sensor is powered with a direct current voltage, you may be out of luck. However, here are some possible 'fixes'.

I read that the phone company, many years ago, had a problem with corrosion and switched from a negative ground to a positive ground, which helped to solve their corrosion problem. If you could insure the system is + grounded, this may help.

I think that most serious outside systems use AC sensors, and if they use DC, employ a positive ground, and are not powered unless a measurement is needed.

This is in response to the Fabian Hoffmann question about electron micrographs. We perform limited "community service imaging" of the type Fabian describes for school projects. We would need to know the scope of the project (usually just a few micrographs). Do let us know of your interest. www.marshall.edu/mbic/

Fritz, all you need is an appropriate 3-terminal voltage regulator to protect your Arduino boards. I don't know what voltage your board needs, so I suggest integrating an LM317T programmable regulator between the board's power jack and the board. The regulator will take the wall-wart's high voltage and reduce it to what the board requires. To program the regulator, connect it between the wall-wart and your board's DC input using this diagram as a guide:

Wiring isn't too critical (point-to-point), but keep lead lengths as short as practical. Be sure to include the 2 capacitors as they'll help "keep things stable" and prevent unwanted high-frequency oscillations. NOTE: the voltage rating of C2 should be above 24V as it's typically an electrolytic. Variable resistor R2 will let you dial in the output to what your board requires. BE AWARE: Keep the maximum current draw ** BELOW 1 AMP **, use a heat sink on the regulator (a TO-220 type clamp-on will be sufficient) and keep the regulator's input voltage BELOW 35 VDC!

If you don't want to bother with a variable resistor for R2, visit www.reuk.co.uk/LM317-Voltage-Calculator.htm as it has a nice table of standard resistor values to use for R1 and R2 for programming various output voltages (and other good info on the regulator).