Simple front end circuit recommendation?

• posted

I?m looking for the simplest circuit that would achieve the followi ng please. SUPPLY:

18V DC, possibly from two PP3s.

INPUT: A high or low going DC voltage, with max of 5-15V, with varying input imped ance, say 1k < 1M. Two input ports, with only one in use of course. (I? ??m assuming it?s impossible or complex to achieve with only one input for the two polarities.)

TWO OUTPUTS: One low going, the other high going, both at lowish impedance, day 470R .

All suggestions would be much appreciated please.

Terry, UK

• posted

mandag den 30. marts 2020 kl. 19.18.59 UTC+2 skrev snipped-for-privacy@gmail.com:

edance, say 1k < 1M. Two input ports, with only one in use of course. (I? ??m assuming it?s impossible or complex

• posted

edance, say 1k < 1M. Two input ports, with only one in use of course. (I? ??m assuming it?s impossible or complex

Terry, that's confusing. Can you write an equation that relates the outputs to the input?

George h.

• posted

mpedance, say 1k < 1M. Two input ports, with only one in use of course. (I ?m assuming it?s impossible or complex

.

Or even a more clear English description. What is a "high or low going DC voltage"? Do you mean of either polarity?

Is the output intended to be both positive and negative? What voltage? Th e same as the input? Lower than the input?

If you are asking for a circuit that accepts low current inputs and higher current outputs at the same voltage without another power supply you ain't going to find it.

```--
Rick C.

- Get 1,000 miles of free Supercharging ```
• posted

A quad op amp, with two sections used as voltage followers, and two as inv erters should suffice. You'd need to switch one or the other of the follower out puts to the cascaded inverters.

Something like TL064 would be relatively easy on the battery power.

For preference, I'd want to do some attenuation (even if the inputs tolerat e

5-15V, making the outputs drive that full range can be problematic). So, maybe the first inverter can be a gain-of-0.5. An array of 5 matched resistors will be the passive component complement.

If you intend +15V to -15V input range, the power supply will have to be

+/-15V, and not +/- 9V.
• posted

Thanks, I?ll try that 064 idea tomorrow if I have any at hand. If n ot maybe I can adapt a couple of 741s.

Terry

• posted

George,

Not confident I can condense it to an equation, but I?ll have anoth er stab at describing what is essentially just a simple DC voltage follower plus inverter. One input A and two outputs B and C. Typical input sources might be from a simple micro switch, PIR sensor, IR Detector, etc. In broad terms, pulses. Either high or low going. Typically fast enough to make a S chmitt unnecessary. Capable of say at least 30mA output.

Supply would be either from my bench unit or an internal battery (or two fo r 18V). Obviously Vcc would determine the allowable input level and the max imum output level.

I envisage a small case with an input phono on one side and two output phot os on the other, with Vcc to a fourth.

I already have various devices, typically made a few decades ago in 2oz tob acco tins, that could achieve the same purpose, but they?re mostly more versatile/complex. This project is for a compact ultra simple, no-brai ner tool.

Terry

• posted

ther stab at describing what is essentially just a simple DC voltage follow er plus inverter. One input A and two outputs B and C. Typical input source s might be from a simple micro switch, PIR sensor, IR Detector, etc. In bro ad terms, pulses. Either high or low going. Typically fast enough to make a Schmitt unnecessary. Capable of say at least 30mA output.

for 18V). Obviously Vcc would determine the allowable input level and the m aximum output level.

otos on the other, with Vcc to a fourth.

obacco tins, that could achieve the same purpose, but they?re mostl y more versatile/complex. This project is for a compact ultra simple, no-br ainer tool.

Are the outputs digital or analog voltages? If analog then some opamp as whit3rd said. 18V and 500 ohms is 36mA so pick an opamp with enough current drive.

George H.

• posted

They follow the inputs, which are analog.

• posted

nother stab at describing what is essentially just a simple DC voltage foll ower plus inverter. One input A and two outputs B and C. Typical input sour ces might be from a simple micro switch, PIR sensor, IR Detector, etc. In b road terms, pulses. Either high or low going. Typically fast enough to make a Schmitt unnecessary. Capable of say at least 30mA output.

o for 18V). Obviously Vcc would determine the allowable input level and the maximum output level.

photos on the other, with Vcc to a fourth.

tobacco tins, that could achieve the same purpose, but they?re mos tly more versatile/complex. This project is for a compact ultra simple, no- brainer tool.

LM8272 is a good choice able to drive well above 36 mA. It also drives a c apacitive load without stability issues which may be important if you are d riving long wires or coax. It's a dual so you only need one. However, it only comes in a surface mount package, MSOP8. The similar LM7322 comes in an 8 pin SOIC which is much larger even if not a DIP.

```--
Rick C.

+ Get 1,000 miles of free Supercharging ```
• posted

:

another stab at describing what is essentially just a simple DC voltage fol lower plus inverter. One input A and two outputs B and C. Typical input sou rces might be from a simple micro switch, PIR sensor, IR Detector, etc. In broad terms, pulses. Either high or low going. Typically fast enough to mak e a Schmitt unnecessary. Capable of say at least 30mA output.

wo for 18V). Obviously Vcc would determine the allowable input level and th e maximum output level.

photos on the other, with Vcc to a fourth.

z tobacco tins, that could achieve the same purpose, but they?re mo stly more versatile/complex. This project is for a compact ultra simple, no

-brainer tool.

Oh but single supply. So V_in(t) is always positive and VA_out = V_in and VB_out = 15V - V_in (you could have some offset other than 15V) Is that right?

George H.

• posted

Yes, that's correct.

I've breadboarded a simple 741 voltage follower with a 0-18V supply, split with two 470R resistors, followed by an NPN buffer with 270R in its emitter. Output is about 0.4V below input and follows it from about

2V to 16V (acceptable for my purposes), delivering about 80mA.

I now need to add an equally simple inverter circuit.

Will probably not incorporate internal batteries after all. For relatively infrequent use away from my workbench I'll just rig up a couple of series PP3s to a phono socket.

P.S. Ruled out 064 etc as I try to avoid the inconvenience of dual polarity supplies.

Terry

• posted

ote:

ve another stab at describing what is essentially just a simple DC voltage follower plus inverter. One input A and two outputs B and C. Typical input sources might be from a simple micro switch, PIR sensor, IR Detector, etc. In broad terms, pulses. Either high or low going. Typically fast enough to make a Schmitt unnecessary. Capable of say at least 30mA output.

r two for 18V). Obviously Vcc would determine the allowable input level and the maximum output level.

put photos on the other, with Vcc to a fourth.

2oz tobacco tins, that could achieve the same purpose, but they?re mostly more versatile/complex. This project is for a compact ultra simple, no-brainer tool.

I think that's easy. Single supply say +18V and ground. V-in goes to an inverting input through R (and R feedback.. an inverting amp) now make a 15V reference and apply that to the non-inverting input. (I think that works...) (I'm sure someone will correct me if it doesn't) George H.

• posted

ote:

ve another stab at describing what is essentially just a simple DC voltage follower plus inverter. One input A and two outputs B and C. Typical input sources might be from a simple micro switch, PIR sensor, IR Detector, etc. In broad terms, pulses. Either high or low going. Typically fast enough to make a Schmitt unnecessary. Capable of say at least 30mA output.

r two for 18V). Obviously Vcc would determine the allowable input level and the maximum output level.

put photos on the other, with Vcc to a fourth.

2oz tobacco tins, that could achieve the same purpose, but they?re mostly more versatile/complex. This project is for a compact ultra simple, no-brainer tool.

If you are using two batteries, you already have a split supply. If you d on't split the supply, how will you support positive and negative outputs?

```--
Rick C.

-- Get 1,000 miles of free Supercharging ```
• posted

have another stab at describing what is essentially just a simple DC voltag e follower plus inverter. One input A and two outputs B and C. Typical inpu t sources might be from a simple micro switch, PIR sensor, IR Detector, etc . In broad terms, pulses. Either high or low going. Typically fast enough t o make a Schmitt unnecessary. Capable of say at least 30mA output.

(or two for 18V). Obviously Vcc would determine the allowable input level a nd the maximum output level.

utput photos on the other, with Vcc to a fourth.

in 2oz tobacco tins, that could achieve the same purpose, but they? re mostly more versatile/complex. This project is for a compact ultra simpl e, no-brainer tool.

Works to do what? Doesn't he want complementary outputs?

This is starting to remind me of the customers in the YouTube video "The Ex pert". "Three red lines made with green ink."

```--
Rick C.

-+ Get 1,000 miles of free Supercharging ```
• posted

have another stab at describing what is essentially just a simple DC voltag e follower plus inverter. One input A and two outputs B and C. Typical inpu t sources might be from a simple micro switch, PIR sensor, IR Detector, etc . In broad terms, pulses. Either high or low going. Typically fast enough t o make a Schmitt unnecessary. Capable of say at least 30mA output.

(or two for 18V). Obviously Vcc would determine the allowable input level a nd the maximum output level.

utput photos on the other, with Vcc to a fourth.

in 2oz tobacco tins, that could achieve the same purpose, but they? re mostly more versatile/complex. This project is for a compact ultra simpl e, no-brainer tool.

Thanks George, but the following seems to work OK: