Power consumption of astable multivibrator

[Ahmedbadr132]

TL;DR Summary

Does the timer555 consume power while the diode is off in the astable multivibrator??

Hi
I was wondering about the astable multivibrator .
Does the circuit consume power while the diode if off ?
If yes how much ?
Please explain in detail.
Thanks

 

[Baluncore]

Welcome to PF.

Yes it does.
What diode? Do you mean the collector of the discharge transistor, on pin 7 ?

There are three internal resistors used to generate the Vcc/3 and 2·Vcc/3 voltages for the two internal voltage comparators.
In the NE555, those resistors have a value of about 5k each, the three = 15k.
For Vcc = 15 volts, the current will be ≈1 mA. That current flows continuously.

 

[BvU]

I was going to ask the same question: what diode ?

(from here)

 

[Ahmedbadr132]

I mean the LED

 

[Baluncore]

I mean the LED

Then you should attach a circuit that shows how the LED is connected.

 

[BvU]

I mean the LED

what LED ?

 

[Ahmedbadr132]

what LED ?

If the circuit is used to power a LED in the astable multivibrator mode

 

[BvU]

Please explain in detail.

@Baluncore already quoted the 1 mA over the three internal resistors.
The other internal cicuits will also draw some current here it has another 1 mA for a total of 2 mA

Perhaps the data sheet has more info. Best thing to do is of course measure.

$\$

 

[Baluncore]

Does the timer555 consume power while the diode is off in the astable multivibrator??

The LED is external to the 555, so the LED power is not consumed by the 555.
The 555 effectively connects the LED to the supply rail.
The R+R+C external time setting circuit also consumes power.

The internal resistor chain, and the internal circuit bias, consume power.

 

[Ahmedbadr132]

Thank you all for replying
So i should now multiply the value of Vcc with 2mA to find the power consumed by the circuit??
Sorry for bad english

 

[Ahmedbadr132]

Can we operate a small motor at 200mA??

 

[Baluncore]

Can we operate a small motor at 200mA??

Probably not.
The 555 output current is usually limited to 200 mA under perfect conditions, which will not always prevail. The start current of a DC motor will be higher.

An inductive load, such as a motor, will require diodes to protect the semiconductor driver. A brush motor will produce significant noise spikes on the supply.

To drive a motor, follow the 555 with an N-channel MOSFET and a flyback diode.

 

[Ahmedbadr132]

Ok
Look
This is what i want .
I want to make a linear dc small motor that works in an intermittent fashion . So i wanted to use the timer555 . Can you please tell me about the best way to do this so i consume the lowest amount of energy from the battery . I actually want the battery to live for 20 years .And i want the linear motor to move 250 times a day . This is my project .

 

[Baluncore]

When the motor moves, how long will it run for, how many turns?
Do you want the motor to go backwards and forwards, or only one direction?

The 555 timer and DC motor is probably not the most efficient way to do it. A stepper motor, controlled by a microcontroller, would be a lower power solution. That could go to sleep on 10 uA, then wake exactly when needed.

Perhaps you might tell us why you want to do this. There may be an existing solution available. What do you need to do? Why?

 

[Ahmedbadr132]

When the motor moves, how long will it run for, how many turns?
Do you want the motor to go backwards and forwards, or only one direction?

The 555 timer and DC motor is probably not the most efficient way to do it. A stepper motor, controlled by a microcontroller, would be a lower power solution. That could go to sleep on 10 uA, then wake exactly when needed.

Perhaps you might tell us why you want to do this. There may be an existing solution available. What do you need to do? Why?

Ok
It is difficult to communicate my design now.
But it consists of a linear motor that moves backwards and forwards . It will move one cycle backwards and forwards and then stantd still for five minutes and repeats .
I want an approximate and primitive estimation of the power requirements.
Thanks

 

[Baluncore]

What does it move?
How far does it move?
How much does the load weigh or what force is applied?
Is it balanced?

 

[Ahmedbadr132]

It moves a small mechanical load maybe 0.5kg
It moves 30 cm
It is balanced

 

[Baluncore]

I actually want the battery to live for 20 years .And i want the linear motor to move 250 times a day .

20 years * 365.25 * 250 = 1,826,250.

We do not discuss perpetual motion machines on this forum.

 

[berkeman]

I actually want the battery to live for 20 years .And i want the linear motor to move 250 times a day .

https://all-car-news.com/en/tesla-powerwall-a-tesla-battery-for-your-wall-at-home-autorai-tv/

 

[Ahmedbadr132]

20 years * 365.25 * 250 = 1,826,250.

We do not discuss perpetual motion machines on this forum.

What do you mean ??

 

[Baluncore]

What do you mean ??

A battery that will last 20 years. How will it be recharged?
Hardware that will reverse 2 * 1,826,250 = 3,652,500 times without wearing out.
How will the mechanism be lubricated?

 

[Ahmedbadr132]

A battery that will last 20 years. How will it be recharged?
Hardware that will reverse 2 * 1,826,250 = 3,652,500 times without wearing out.
How will the mechanism be lubricated?

The battery can be recharged .
Some linear motors work for 100,000,000 cycles .

 

[Baluncore]

@Ahmedbadr132
I suspect you have little experience in this field. There are very many things that need to be considered in this design project that have not been mentioned.

The closer one tries to get to an optimum design, the more interfaces and mismatches one must remove. That requires knowing what is required and why. You have not told us what you are trying to do, or why. That prevents our optimisation of the design in at least two different ways, a design path that will lead to a probable failure.

If it is so secret or commercial that you cannot tell us what it is for, then you will not get a good result when you ask us to design it for you, and we are wasting our time trying to help.

Can you say how many hundreds, or thousands of these devices you intend to manufacture?

 

[Ahmedbadr132]

Well
I am hoping to create a device that will help 1 million american diagnosed with hydrocephalus . For this i will need to implant a linear motor under the skin of the patient . I want to charge the battery wirelessly with resonant-link and the battery with the motor should last at least 20 years

 

[berkeman]

diagnosed with hydrocephalus . For this i will need to implant a linear motor under the skin of the patient

That's a noble purpose indeed. But is this a new type of treatment? Are you working with MDs on this new treatment modality? I didn't see it mentioned in my brief search of the disease and its treatments...

https://www.ninds.nih.gov/health-information/disorders/hydrocephalus

Surgery to treat hydrocephalus involves two options:

1. A shunt (tube) is surgically inserted into the brain and connected to a flexible tube placed under the skin to drain the excess fluid into either the chest cavity or the abdomen so it can be absorbed by the body.

2. Endoscopic Third Ventriculostomy (ETV) improves the flow of CSF out of the brain. A tiny hole is made at the bottom of the third ventricle and the CSF is diverted there to relieve pressure. Sometimes this is done in conjunction with choroid plexus cauterization to try and decrease the production of CSF.
** Choroid plexus cauterization uses electric current to burn the CSF-producing tissue
(i.e., the choroid plexus) in the lateral ventricles in the brain, so it produces less CSF.

Shunt systems generally function well but they can fail to properly drain the CSF due to mechanical failure or infection. When this happens the CSF builds up in the brain again and earlier symptoms may recur. To reduce the buildup of CSF, the clogged shunt system is replaced to restore drainage of CSF.

Shunts require monitoring and regular medical checkups. Multiple surgeries may be needed to repair or replace a shunt throughout a person's lifetime. People should seek medical help immediately if symptoms develop that suggest the shunt system is not working properly.

 

[Baluncore]

I would expect the failure rate of a shunt, to be less than that of, a shunt with a peristaltic pump.
Hydrocephalus implies that positive pressure is a problem.
Is there a situation where additional mechanical pumping is required?

 

[Ahmedbadr132]

I would expect the failure rate of a shunt, to be less than that of, a shunt with a peristaltic pump.
Hydrocephalus implies that positive pressure is a problem.
Is there a situation where additional mechanical pumping is required?

Why do you continue to disappoint me .
We need the battery to last for 20 years and the linear motor can work for 100 million cycles .this is the only requirement .

 

[hutchphd]

I can design such a device: it will fit in a small suitcase.
Obviously that is not the only requirement. If you are asking a question, it behooves you to carefully listen to the answer. If you know enough to dismiss the answer, why are you asking the question?

 

[Ahmedbadr132]

Human have different ways of thinking as well as different beliefs .
the only thing i need is to know the power require ment of the linear motor and a way to control it as i said above

 

[Baluncore]

the only thing i need is to know the power require ment of the linear motor and a way to control it as i said above

This is a bigger project than you imagine. Before it could happen, every challenge must be resolved. As you gain more experience, you will become aware of the complexity. That is perfectly normal. It is called the Dunning-Kruger effect.

You want to eat an elephant, one bite at the time. Design of the pump and motor will be a challenge. Once they are designed, the controller can be designed. Only then can we know the power consumption.
Now that I know where the journey would take us, I can see the minefields ahead. Do we need to walk through the first minefield? I prefer to keep it simple, and go around.

One critical thing about the pump will be making sure there is never any counterflow that could allow an infection of the CSF. The pump will need two automatic valves, with the volume between those varying cyclically. What will the maximum flow rate be? If a pump fails, will both valves remain open as CSF pressure drives fluid through the pump?

My associates do not supply the US market, simply because of the cost of the insurance needed to do business in a litigious society, we don't need that. Anywhere else is less risky and less expensive.

PF must discourage dangerous activities that might do harm. Before you embark on this project, you need legal advice on liability protection in the medical field.

 

[hutchphd]

The worst problems occur when you don't even realize what you don't know. Please seek and heed advice.

 

[berkeman]

Thread closed temporarily for Moderation...

UPDATE -- This medical project is beyond the capabilities of the OP, so the thread will remain closed.