# Tag Info

31

Why did you leave out C3? From Charles Platt's Make: Electronics (1st edition): There is a reason for everything in an electronic circuit (and Platt did explain why it is needed). You have learned this the hard way. From p155: Set your power supply to deliver 9 volts. It will be convenient for this experiment if you supply positive down the righthand side ...

19

The 555 was designed in the late 1960s - early 1970s, then the usual design method for analog ICs was in a nutshell: think up and draw the block diagram translate the blocks from the block diagram into discrete transistor based circuits (resistors and capacitors can be used as well). For some situations you might want to use special test-ICs that contain ...

16

When the oscillators operate and switch the LEDs on and off, they will be creating voltage ripples on the power supply as the current demand changes. These voltage ripples can then cause other devices on the same power rail to malfunction. As mentioned in the comments, add a decoupling capacitor across the power pins on each of the 555 timers. A value of 0....

12

If you want to know what methodology was used, I suggest you read the book written by the creator of the NE555, Hans Camenzind (RIP). The link above is for a free download. You can also buy the printed book. I have both his books in hardcover. Edit: Jim Williams (RIP), Analog Circuit Design is good too, it's a series of chapters by different folks, including ...

10

The 555 timer uses an analog RC as its timebase, but that's never going to be very stable. Even with high precision resistor (0.01%) and capacitor (10%), there is poor initial accuracy and significant drift with temperature. There are improvements such as Analog Devices LTC6900CS5#TRMPBF, which can generate 20kHz using a single 100k resistor to determine the ...

10

They are both connected to same power supply with long wires. Wires have inductance. The 555 oscillators oscillate and when they toggle state they can take a short but high current spike from the power supply. As inductance prevents high frequency currents, the supply voltage at the chips can dip every time they toggle. Dips in the supply voltage are common ...

8

There is no poltergeist in the breadboard, the poltergeist is the breadboard and they are notorious for their parasitic values that can create headaches for designers . The circuit looks like this: simulate this circuit – Schematic created using CircuitLab The resistance and inductance are from the breadboard rails, not to mention nF's of cross ...

6

It's used for the same sort of stuff you'd use it for on the ground. As a timer, as an oscillator, for pulse generation, as a watchdog timer... you have many of the same needs aboard a spacecraft as in any other type of electronic system. For most space missions, designers will specify uprated, space-qualified versions of standard parts. TI sells one such ...

5

I'll start with the 555. The circuit around the 555 is pretty much just the classic "astable multivibrator" circuit as given in the 555 datasheet: $R_A + R_B$ in combination with $C$ sets the frequency. If you change $R_A$, then you change the frequency of the oscillator. $R_A$ sets the current used to charge $C$. More current (lower \\$...

5

It's a level-sensitive (level-triggered) latch (or level triggered flip-flop). I don't think it really helps to get bogged down into the definitions and taxonomy in this kind of thing unless you have some authoritative source to point at that is respected as such. Terminology evolves and the 555 is an ancient IC. An R-S flip-flop is the same thing as an SR ...

4

If I understand your application correctly you can use an edge-triggered monostable multivibrator, for example 74LVC1G123. As shown in the TI datasheet, figure 2, it is possible to have an output pulse shorter than the input pulse: If the timing jitter (delay from the input to output) isn't too critical, you could also consider using a tiny microcontroller....

4

If you establish a certain voltage Vc at the control pin, either with a stiff voltage source or some kind of network of resistors or whatever, then the capacitor charges from that Vc/2 up to Vc and discharges back to Vc/2. Note that the resistor values are not well specified, 5K is a 'typical' value, but they are well-matched to each other. (Looking into the ...

4

The NE555 is not great for this kind of a application, though 10% is a bit much for "typical" error. I would expect it to typically be within a few percent and maybe change a few percent more over temperature and a couple percent more with worst case timing component values. The bipolar version also draws large current surges at switching which can ...

4

You mustn't be switching VCC! By doing that you're relying on the power-up behaviour of the ICM7555 every time. And that's undefined, far as I read the datasheet. So, what happens isn't that surprising: you're taking away the power supply, and that puts TR, CV, DIS and THR all above the supply voltage. That is outside of what is allowed for operation. In ...

4

There's no single answer to your question. It's a mix of the maximum speed of the transistors involved, limits put by maximum currents you want to carry on an IC, the parasitics you can't wish away in the olden packages that 555s are often sold in, the fact that for higher speeds, you'll need smaller capacitors, which means they are less large compared to ...

3

A flickering or flashing UV LED will be more noticeable than one that is continuously on at low power. Just use a resistor from the forklift's 12V to power the LED

3

Trying to use NE555 timer in astable mode along with d-flip-flop to monitor activity with minimal components for this purpose. I count two different supplies, and ten components (aside from the LED and its series resistor). You forgot to add decoupling to your flipflop's and your 555's supply, too. A 50 ct microcontoller + one decoupling cap would do better ...

3

The circuit is theoretically correct, the faults are probably due to the assembly. (Is R2 likely to be connected to the Discharge pin?) R1 is not required for proper operation at all. The frequency depends on R4 and the duty cycle is always 50%. EDIT: NE555 at 3V. You built it well and measured accurately. :) The NE555 need a minimum operating voltage of 5V....

3

You could use a Monostable Pulse Generator like the LTC6993, which generates a programmable pulse width of 1 us to 33.6 s, which covers the 500 us that you need. Check pages 12 and 13 of the datasheet to program the pulse width.

3

Is there any way to remove the wave before 2 ms or is there anyway to make it same as the rest in the graph. Yes. First, you remove your NE555 from your design approach. It doesn't help you in any way I can think of when trying to convert a sine wave to an impulse comb. Then, you remove the 741. It doesn't help you in any way when trying to convert a sine ...

3

To understand how C1 is discharged, you need to first understand how the 555 timer works. The 555 timer has a resistor divider with 2 taps and 3 equal value resistors which creates two reference voltages equal to 1/3 of VCC and 2/3 of VCC. If the voltage at the trigger input (pin 2) goes above 1/3 of VCC, the set input of the latch goes high and the output ...

3

the frequency changes from 650 Hz to 1440 Hz according to R1 potentiometer and duty cycle changes with R2 potentiometer.

3

The diagram below shows an (untested) example of a circuit which may achieve your aims. (The somewhat non standard 555 pin layout is the schematic editors idea.) Apart from the 2 potentiometers and switching transistors operation is standard 555 astable. The timing capacitor Ct charges via either Rchg1 or Rchg2 (see below) in series with Rdis until the ...

3

A 555 seems to be the wrong choice here – either you're building something open-loop, in which case you'll have no feedback and no real regulation, or you're building something closed loop, and then your 555 becomes nothing but an inelegant method to solve a small subproblem of the overal converter problem; you'd simply not do that. Instead, you'd use one of ...

3

Any 555 calculator website can do this for you, but the results will be questionable. To start, put in 10 K for Ra and 100K for Rb, and then adjust them until you get the output parameters you want. Another approach is to use the equations in the 555 datasheet and calculate the resistor values directly. BUT - your post indicates that you want results that ...

3

Most microcontrollers have a PMW/Counter logic block available that runs independently of the CPU. Check the datasheet to see if that's available on your micro, it's free and easy.

3

Your spikes have at least THREE possible causes where you tie the Scope Probe GROUND lead (but you can also HEAR this) lots of wiring inductance; you can reduce this, by using TWISTED PAIRS to provide Hot/Return paths no local provision for charge directly where needed; this requires a SHUNT capacitor no series impedance (inductor or resistor) in the VDD ...

3

The fact that the DAC0800 specifies needing at least +/- 4.5V means that you will not be able to run this chip with a 6V source (at least not to spec). You can DC bias this part to "fake" a bipolar supply but you will need at least a 9V supply to have the headroom to swing. If possible, try to stick to any of the manufacturer's reference designs as ...

3

The use of this capacitor is discussed on page 5 of the datasheet you linked. Whether or not you need this capacitor depends on your application and its requirements.

3

Generally you should add it, 10nF is usually enough. The CMOS 555 has a high input impedance on the control voltage input, so EMI can affect the timing cycle even if the supply voltage is very stable. The 555 timer circuits do not have internal references so the timing is affected both by noise on the divider chain and by any changes in the supply voltage ...

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