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I have a simple analogue circuit I'm trying to create. Essentially it's a 1.2V power source that pulsates a vibrator motor - without a 555 timer.

When the circuit is closed, uninterrupted current is fed through the circuit but along one route I would like to pulsate current to a vibrator motor (at a rate of around once per second).

Intuitively, this seems possible through some sort of capacitor and maybe modulating the charge rate (pulse frequency) via a resistor in series, but I am unsure of the exact details.

I'm seeking help in identifying the types of components required to achieve this effect.

A component that can momentarily store and release energy, of which the frequency can be modulated?

Here's a simple diagram of the circuit in question.

enter image description here

Thanks!

EDIT:

Further details:

The vibrator motor is rated at 1.3V, 70mA

I would like it to pulse once every 1 or 2 seconds (Exact number will depend on how much this effects the speed of the coil reaching desired temp).

The specifications of the heating element are unimportant at this point. In hindsight, that part of the circuit can be ignored.

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    \$\begingroup\$ You have a badly defined requirement for something or other and a circuit that is confusing. How can a confusing circuit (that talks about a low capacity super capacitor) possibly be matched to an under-defined requirement. Concentrate on the words that describe what you want and leave your circuit guesses somewhere else. \$\endgroup\$
    – Andy aka
    Commented Jan 31, 2020 at 9:09
  • \$\begingroup\$ I was really hoping people could read my novelty in circuit design. I'm not here to try and teach the community something, I'm looking for help and advice. I used the term "super capacitor" because I know these are synonymous with energy retention but I'm dealing with single digit voltage so I presume I would need to define a super capacitor denoted for low voltage. It's a really simple circuit design, I don't deem another 4 years on top of my current 7 of Uni necessary to climb this mountain. \$\endgroup\$
    – Edward
    Commented Jan 31, 2020 at 9:18
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    \$\begingroup\$ You don't need another 4 years of Uni, you need a 555 Timer. \$\endgroup\$
    – VBwhatnow
    Commented Jan 31, 2020 at 9:46
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    \$\begingroup\$ Analog or digital doesn't matter. An continuous oscillator circuit of any type at any frequency needs active components of some kind - chips, transistors. When you hit a bell once with a hammer, it does not ring continuously because it cannot. \$\endgroup\$
    – AnalogKid
    Commented Jan 31, 2020 at 12:15
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    \$\begingroup\$ The 555 is not a logic gate. It is a timer, designed to do pretty much what you need - generate on and off pulses at a specific frequency. It won't work properly at low voltage though, so you can't use it when you only have a 1.2V power source. Simply using a capacitor won't get you the pulsing you want, though. You need an oscillator driving a switch to do what you want. If you have access to a higher voltage, then it is easier. If not, your oscillator will have to be designed with the low voltage in mind - and that can be tricky. \$\endgroup\$
    – JRE
    Commented Jan 31, 2020 at 12:25

2 Answers 2

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You can use a TLC551 and a MCH3383 p-channel MOSFET. It will work down to 1V.

Follow the astable multivibrator equations in the TLC551 datasheet, and drive the MOSFET gate with the output. MOSFET source to +1.2, drain to motor, other side of motor grounded. Reverse biased 1N4148 or BAT54 across the motor. Done.

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You can't do this with purely passive components, period.

You probably should use a dedicated timer IC. They're extremely cheap and ubiquitous, and perfect for exactly your application.

If you absolutely must go 'strictly analog', you can do this with an op amp circuit called a Wien bridge oscillator. You will have to increase your supply voltage to make this work. Be sure to use a 'rail to rail' op amp if you choose to attempt this.

schematic

simulate this circuit – Schematic created using CircuitLab

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  • \$\begingroup\$ Neither the 555 nor most opamps will work at 1.2V, as the OP seems to require. \$\endgroup\$
    – JRE
    Commented Jan 31, 2020 at 17:19
  • \$\begingroup\$ I realize this, which is why I suggested OP relax this requirement in my answer. \$\endgroup\$
    – Ocanath
    Commented Jan 31, 2020 at 17:22
  • \$\begingroup\$ Follow up, there are relatively cheap op amps that can operate rail-to-rail sub 1V for operation with a single cell alkaline battery (for example, the NCS2001). I believe this circuit could work at 1.2V if paired with a small nMOS that has a low gate threshold voltage (such as the BSH105). \$\endgroup\$
    – Ocanath
    Commented Jan 31, 2020 at 17:37
  • \$\begingroup\$ edited to reflect the fact that a 555 timer specifically wouldn't be a good fit, given the requirements \$\endgroup\$
    – Ocanath
    Commented Jan 31, 2020 at 18:19

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