Making pusle generator

Thread Starter

Jaimeperezjy

Joined Jan 8, 2020
12
Anyone have some insight on this build right here. Don't know the capacitor size. And the potential meter is the kind that starts low and rises as you turn it. I was told there's linear and audio. Don't know much on that. Looks like a 555 chip, resistors I think I can identify using colors. Led that flashes faster the more you turn it up. And has what seems to be tv antenna cable for the loop
 

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eetech00

Joined Jun 8, 2013
1,836
Anyone have some insight on this build right here. Don't know the capacitor size. And the potential meter is the kind that starts low and rises as you turn it. I was told there's linear and audio. Don't know much on that. Looks like a 555 chip, resistors I think I can identify using colors. Led that flashes faster the more you turn it up. And has what seems to be tv antenna cable for the loop
:confused:
Soooo....what is your question?

eT
 

MrChips

Joined Oct 2, 2009
20,216
Welcome to AAC!

Okay. Let's get a few things straight.

1) A potential meter is something that measures potential, such as a voltmeter. What you mean is a potentiometer (also called pot for short, not the kind you smoke) also known as a variable resistor.

2) There are linear pots and audio pots (also known as log pots or log taper).
A pot is also known as a voltage divider or sometimes a volume control.
A pot is a variable resistor. This means that the resistance changes depending on the position or rotation of the control knob (sometimes it is a slider or a screwdriver setting).

A linear pot is one where the resistance is proportional to the position (or angle of rotation) of the control knob.
An audio pot is one where the resistance starts low but then increases much faster as the control knob is turned. In other words, it is non-linear. Volume controls tend to be log taper pots for good reason. (You can also get reverse log taper but you may as well ignore that one.)

Depending on the type of control you need, you can choose linear or audio taper. For now, you can stick with linear taper.
 

Thread Starter

Jaimeperezjy

Joined Jan 8, 2020
12
Welcome to AAC!

Okay. Let's get a few things straight.

1) A potential meter is something that measures potential, such as a voltmeter. What you mean is a potentiometer (also called pot for short, not the kind you smoke) also known as a variable resistor.

2) There are linear pots and audio pots (also known as log pots or log taper).
A pot is also known as a voltage divider or sometimes a volume control.
A pot is a variable resistor. This means that the resistance changes depending on the position or rotation of the control knob (sometimes it is a slider or a screwdriver setting).

A linear pot is one where the resistance is proportional to the position (or angle of rotation) of the control knob.
An audio pot is one where the resistance starts low but then increases much faster as the control knob is turned. In other words, it is non-linear. Volume controls tend to be log taper pots for good reason. (You can also get reverse log taper but you may as well ignore that one.)

Depending on the type of control you need, you can choose linear or audio taper. For now, you can stick with linear taper.
Thank you! I thought something was wrong there . The only thing I can't figure out is what size capacitor I need. I got everything else narrowed down. The previous one I have still works but I need to recreate it. The current one blinks, the new one I'm making doesn't blink. I Kno for sure it's the capacitor. Any thoughts on which one I should use?
 

dendad

Joined Feb 20, 2016
3,316
See if you can draw out the circuit for a start. Then check to see if it has been built along the lines of a Googled 555 flasher circuit.
 

MisterBill2

Joined Jan 23, 2018
5,189
"A hall effect signal generator"???? That does not make any sense at all. I have heard of a Tunnel Diode signal generator, but that was a poor choice of a project by any standard.
If you want to make a signal generator there are three things that must be defined first.
1. Frequency, or frequency range.
2. The output signal amplitude and power level
3. The type of waveform, sine wave, square wave, pulse, triangle, or some other shape.
After that come details like stability, control, and power supply source.
THEN we can point you toward a circuit that will provide what you asked for.
 

Thread Starter

Jaimeperezjy

Joined Jan 8, 2020
12
"A hall effect signal generator"???? That does not make any sense at all. I have heard of a Tunnel Diode signal generator, but that was a poor choice of a project by any standard.
If you want to make a signal generator there are three things that must be defined first.
1. Frequency, or frequency range.
2. The output signal amplitude and power level
3. The type of waveform, sine wave, square wave, pulse, triangle, or some other shape.
After that come details like stability, control, and power supply source.
THEN we can point you toward a circuit that will provide what you asked for.
Basically what I need is something that throws pulses just like a distributor on a car does. Mine seems to be wired as a flashing led 555 but with a few extra wires and soldering. I will post a drawing once I get home
 

MisterBill2

Joined Jan 23, 2018
5,189
OK, here is a guess, which is that it is intended to trigger the hall effect pickup in a distributor for an engine ignition system. That means that the magnetic pulses come from an integral coil. It sounds a lot like an ignition system service tool. BUT this is just a guess.
 

Thread Starter

Jaimeperezjy

Joined Jan 8, 2020
12
OK, here is a guess, which is that it is intended to trigger the hall effect pickup in a distributor for an engine ignition system. That means that the magnetic pulses come from an integral coil. It sounds a lot like an ignition system service tool. BUT this is just a guess.
Yes exactly!!!! That's basically what it does. I believe the bigger capitance capacitor will make the pulse longer, I have a 10uf and the light stays solid green. So I'm assuming the pulses are so short I wouldn't be able to really see it.
 

AnalogKid

Joined Aug 1, 2013
8,305
The only missing connection is pin 5, the Control input. Other than that, it is a classic 555 astable with a 1K to Vcc (Ra) and a fixed resistor plus pot in series between 2-6 and 7 (Rb). The pot markings have been sanded off, so we don't know the value or taper.

ak
 

MrChips

Joined Oct 2, 2009
20,216
I don't see Vcc and GND connected to the board.
I see one brown wire connected to the pot. I don't see the other connection to the pot.
Really, the pot should be in series with a fixed resistor.
 

Thread Starter

Jaimeperezjy

Joined Jan 8, 2020
12
Ground was connected but ripped off. And power was connected but also ripped off. You guys think maybe a 250k linear pot would work? I'm going to be trying a 1000uf capacitor, and a 250k pot to see how that turns out
 

MrChips

Joined Oct 2, 2009
20,216
No.
1000μF is to large.
250kΩ pot is too large.

Electronics engineering is a disciplined subject. It does not rely on hit-or-miss trial-and-error.

Show your circuit diagram first.
 

AnalogKid

Joined Aug 1, 2013
8,305
Two basic questions.

1. What is the desired frequency range?

2. What output shape(s) do you want?

Because Ra is so small relative to Rb, the circuit you have makes a square wave that is approximately symmetrical. That is, the output has an approximate 50/50 duty cycle. At the higher frequencies the duty cycle will start to change, with the percentage of time in the high state increasing and the percentage of time in the low state decreasing. There is an alternate astable circuit that uses one fewer resistor and is better at maintaining a near 50/50 duty cycle regardless of frequency. It is on the LMC555 datasheet.

ak
 
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