Step circuit

Thread Starter

karas

Joined Sep 8, 2011
211
Hi I need to build steps circuit the circuit increase one volt each one step and the time for each step is one second,so can someone help me
thanks
 

absf

Joined Dec 29, 2010
1,968
How much current for the output of the voltages stepped and what is the MAX output voltage ? Can you use mcu or just discrete logic chips ?

Allen
 

wmodavis

Joined Oct 23, 2010
739
Maybe not the most optimum solution but might help your thinking process.

Use a binary counter fed by a 1 Hz clock signal and feed the counter outputs into an D/A.
 

crutschow

Joined Mar 14, 2008
34,285
There's no reason to build a complex discrete DAC circuit. Just use a standard 8-bit DAC and toggle only the higher order bits you need to generate the required steps. For example the upper three bits could give you seven 1V steps by proper scaling of the output.

How high do you want these one volt steps to go (what's the maximum output voltage)?
 

Thread Starter

karas

Joined Sep 8, 2011
211
How much current for the output of the voltages stepped and what is the MAX output voltage ? Can you use mcu or just discrete logic chips ?
Allen
it is vey low current (5 milli amp) and max out put voltage is 10 v
 

ScottWang

Joined Aug 23, 2012
7,397
For a not precisely method, using NE555, CD4017 and some 1n4148, some resistors.

NE555(1Hz) → CD4017(counter) → 1N4148 → Voltage divider(resistors) → Vout

1N4148 x10, 10 resistors and one common resistor for voltage divider.
 

crutschow

Joined Mar 14, 2008
34,285
Below is the simulation of a circuit, as Scott suggested, with a 555 clock, a binary counter, and an R-2R ladder network with an op amp and transistor buffer output that gives ten 1V, 1 second steps and then repeats.

Is that more or less what you want?

Edit: The +12V power and ground connections to the counter and the AND gate are not shown.

Note that for best accuracy/stability you can use two 10kΩ resistors in series to make the 20kΩ resistance values. That also simplifies the part's list, although at the expense of more parts.

Step generator.gif
 
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Thread Starter

karas

Joined Sep 8, 2011
211
Below is the simulation of a circuit, as Scott suggested, with a 555 clock, a binary counter, and an R-2R ladder network with an op amp and transistor buffer output that gives ten 1V, 1 second steps and then repeats.

Is that more or less what you want?

Edit: The +12V power and ground connections to the counter and the AND gate are not shown.

Note that for best accuracy/stability you can use two 10kΩ resistors in series to make the 20kΩ resistance values. That also simplifies the part's list, although at the expense of more parts.

View attachment 71799
it works perfect , thanks so much
 

Thread Starter

karas

Joined Sep 8, 2011
211
Below is the simulation of a circuit, as Scott suggested, with a 555 clock, a binary counter, and an R-2R ladder network with an op amp and transistor buffer output that gives ten 1V, 1 second steps and then repeats.

Is that more or less what you want?

Edit: The +12V power and ground connections to the counter and the AND gate are not shown.

Note that for best accuracy/stability you can use two 10kΩ resistors in series to make the 20kΩ resistance values. That also simplifies the part's list, although at the expense of more parts.

View attachment 71799
what is the function of the transistor in the circuit and when Q1 is high what is vbin and vout and also when Q1and Q2 are on what is the value of vbin and vouto
 
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Thread Starter

karas

Joined Sep 8, 2011
211
Below is the simulation of a circuit, as Scott suggested, with a 555 clock, a binary counter, and an R-2R ladder network with an op amp and transistor buffer output that gives ten 1V, 1 second steps and then repeats.

Is that more or less what you want?

Edit: The +12V power and ground connections to the counter and the AND gate are not shown.

Note that for best accuracy/stability you can use two 10kΩ resistors in series to make the 20kΩ resistance values. That also simplifies the part's list, although at the expense of more parts.

View attachment 71799
please what is the values of vbin at different steps and also vout and what is the REASON of USING the transistor
 
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crutschow

Joined Mar 14, 2008
34,285
please what is the values of vbin at different steps and also vout and what is the value of the transistor
The value for Vbin is shown on the graph and is approximately .747 of the desired Vout which is why the op amp has a gain of 1.338. The Vout steps are 1V.

What do you mean by "value of the transistor". It's shown as a 2N2222 but most small NPN transistors will work. Its purpose is to provide more output current than the op amp can supply.

Note that the circuit I posted cycles continuously. If you need it to stop at the end and return to 0V (or stay at 10V) until a switch is actuated to repeat the cycle, then I can modify the circuit for that.
 
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Thread Starter

karas

Joined Sep 8, 2011
211
the value for vbin is shown on the graph and is approximately .747 of the desired vout which is why the op amp has a gain of 1.338. The vout steps are 1v.

What do you mean by "value of the transistor". It's shown as a 2n2222 but most small npn transistors will work. Its purpose is to provide more output current than the op amp can supply.

Note that the circuit i posted cycles continuously. If you need it to stop at the end and return to 0v (or stay at 10v) until a switch is actuated to repeat the cycle, then i can modify the circuit for that.
sorry i mean the reason of using the transistor
 

crutschow

Joined Mar 14, 2008
34,285
sorry i mean the reason of using the transistor
The transistor is a voltage follower to boost the output current since the 5mA you mentioned may be near the limit of what the op amp can deliver. But if the output load is never lower than 2kΩ you can eliminate the transistor and just connect R15 directly to the op amp output.
 
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