Submitting An Electronics Design to a Magazine

I've had maybe a 10 design ideas put in EDN. [My employer required me to do it since it was damn cheap advertising.] You get $100. [I don't know the current fee.] If you read what they publish, you will see not all are from large companies, and many are foreign.

Patents are another story. I wrote a design idea that some company claimed violated their patent. Now this is pure crap since I didn't sell the device on the market, but rather built and demonstated it in the lab. A five minute in the hallway meeting with the director of engineering, employing phrases like damn lawyers, assholes, and bullshit, was held. The nasty-gram was filed, but we never dignified it with a reply.

The key to writing a design idea that will get published is to keep it simple and to keep it "real." By real, I mean something that a large marketplace of readers will find interesting, not some obscure nuance in the dark corners of circuit design. [You want to write like Al Franken, not Noam Chomskey.]

Sensor interface circuits are good for EDN. Everyone understands light, temperature, pressure, weight, etc. Not everyone understands how to convert real life phsyical quantities to electronic signals.

My guess as to no reply is: You didn't submit a design.

You might try

-Bill

I would say this is correct, but for the reason that they are simply too lazy to answer your question. If you sent them the info they _might_ actually acknowledge you. But maybe not.

Magazines are just ignorant. Their attitude seems to be "Give us everything, and if we feel like it, we will give you a small scrap."

I submitted an article to a magazine and asked how they liked it. (If they didn't I would have modified it until they did.) I would have been satisfied with _any_ response, including "buzz off", but it sat in someone's InBox for 10 months, then suddenly appeared in the magazine! No notice, no thank you, (and no check!) I had to pester them for the article payment.

Gary Peek Industrologic, Inc.

Judging from the designs they publish, they're not very picky.

Most of the circuits are:

(1) Very lightly disguised circuits from the National IC app handbook.

(2) Have major typos in the schematic that make the thing not work.

(3) Are yet another "porch light controller with a 555 chip".

(4) Using some single-sourced high-price obsolete IC to do something it wasnt designed for.

(5) No mention of the circuit's power drain, voltage-stability, or temperature stability, all of which are probably really awful.

(6) Uses some $33 Tajikistani thermologicator in place of a 33 cent LM334.

(7) Has no short-circuit, over-temp, RFI, EMI, or self-oscillation control circuitry.

(8) Has a 0.022uF capacitor hanging on the output of every op-amp.

(9) Uses a digital IC as an analog op amp.

(10) Uses an op-amp as a logic gate.

(11) The Pc board layout was laid out mirror-imaged, requiring you to bend all the IC leads over. (Also saw this once on a Jameco Digital clock kit!)

While your comments are hopefully meant to be an exaggeration, the general theme of your post is correct. Digging through the the EDN website, this is the first design idea that I thought warranted publication. I must have rejected 20.

One of my favorite design ideas in EDN was a cheap battery capacity tester using a Walmart alarm clock.

Reading over this best of 20, I just note two things:

The article suggests using a Darlington pair would be one solution. A teensy bit of reflection leads one to realize that makes no difference, the base current error is still there and of the same magnitude. Actually worse, as there's now two base-emitter drops that will vary with temperature.

If you're going to add an op-amp, how about just doing the straight-forward thing and have the op-amp floating and measure the collector current?

Interesting. I used a device level equivalent of Figure 2 around 1970 to accurately measure the current in a HV device (for an automotive ignition application) which only had a beta of *3* ;-)

...Jim Thompson

I'm not sure I understand. The collector current of the driver stage of the Darlington is part of the collector current of the combined device, so the uncompensated error is 1/(beta1*beta2) instead of just 1/beta1.

The V_BE drops reduce the headroom but shouldn't cause additional error, since there's an op amp in there compensating for them.

For good accuracy, you have to drop some voltage across the sense resistor, which costs a bit of headroom, and the big CM swings at the collector could be a problem, depending on the application.

It looks as though the EDN approach would work pretty well for constant currents and slowly-varying loads. Its main drawback is that the compensation has to pass through the main (slow) feedback loop, so that the beta compensation won't work properly with dynamic loads. If the reference voltage varies, this could also cause windup problems when switching from large to small currents.

I'd probably want to measure the base current and use a Howland connected op amp to pull an identical current out of the emitter directly, without messing with the main loop. That inner loop could be extremely fast, because it's doing a small tweak and therefore wouldn't affect the stability of the main loop--and it also isn't slowed down by the slow-as-molasses power BJT. The accuracy would be similar to the original circuit's, and the dynamics significantly better.

Merry Boxing Day, all.

Cheers,

Phil Hobbs

The way I look at it, adding the extra transistor doesnt help anything, as the bottom transistor's base current is still contributing to the emitter voltage being measured. The Darlington hookup only lowers the input base current, not what's being measured.

I'd do the traditional MOS circuit and be done with it.

1. You didn't include their check.

Cheers! Rich

Wait, they had transistors in 1970? ;-)

I first held a transistor in my hand in 1956 ;-)

...Jim Thompson

It was a CK722 and cost $35 each. About $500 in today's dollars.

The really nice thing about germanium transistors is that you did not have to bias them. They self-biased at room temperature.

Does anyone remember a thermometer circuit that used the germanium leakage as the sensor. I built one in the early 60's. As I recall is was very simple with a coil, capacitor and maybe a couple of resistors. I think it was some kind of blocking osc. The temperature dependent leakage charged the cap and at some point the transistor turned on and discharged thru the coil giving a pulse with lots of harmonics that you could pick up as a click on an AM radio. The time between clicks was temperature dependent due to the increased leakage with temperature.

Actually my first was a CK760... my father was a Raytheon wholesaler, so stocked the parts for their AM radios.

...Jim Thompson

I first held an LSI chip in 1976. It was the 1K ram chip, the 2102, for Don's TV Typewriter.

I can still remember staring at the thing-- dumbfounded that there could be 1024 flip-flops in that thing!

Nowadays I buy RAM sticks with 8 billion bits of memory and arent half as amazed. Humans can get used to anything.

I designed my first analog IC in 1963, the MC1530/31 OpAmp.

...Jim Thompson