I am starting to struggle finding a source for more specific components with decent delivery times and postage prices and international shipping.
I'm looking for an LDO with a soft start for my DC motors, but I am really struggling to find any that I can order internationally. Does anybody have any good sources? I don't yet have a tools and experience for onboard components, so one with pins that fit on a breadboard is preferable.
It shouldn't need to support more than 8ish volts max, but wiggle room wouldn't hurt.
I could alternatively make a soft start myself (but I would prefer to keep the circuit smaller with a single chip), but then I am going to need a rail-to-rail op amp that supports significant amounts of Amps. The motor shouldn't produce more than 0.25A once it slow starts nicely and with a few stabilizing caps. But I haven't found any components like this either.
I want a soft start for my DC motors, as I am experiencing too big of a power draw when they instantly start. I can just program in soft starts through the arduino all over the place, but I would prefer the electronics to just handle it.
I got suggested to use a LDO with a soft start (according to TI, LDOs having soft starts is common), so that I get a single chip solution, instead of bloating my circuitboard.
Sorry, forgot mention that I have an input voltage of 8v. Currently enabling the driver simply inputs the full 8 volts to the motor, but I would like to slow start them, all the way up to 8 volts, just to avoid the initial draw spike.
Depending of the performance of the motors/bot in total I might want to regulate the motor input to about 6v later.
Control/regulate the motor with a MOSFET transistor. Slow start ramp can be made in software very simple and requires no extra CPU time. Could be done with a simple counter that increments by interrupt or every time loop is run. The speed will be controlled by the PWM-output.
I know, but I'd like to do it through the electronics. My actual goal is to learn electronics and do as much as possible with just components. I use the ardunio just to generate signals for components that need them, nothing more.
Graylord:
I know, but I'd like to do it through the electronics. My actual goal is to learn electronics and do as much as possible with just components. I use the ardunio just to generate signals for components that need them, nothing more.
OK.
You could do a simple soft start with a R/C-filter before the transistor/MOSFET.
Series resistor from the arduino to a capacitor and then connect that to the base/gate. It will take some time for the capacitor to charge and go to full voltage - in that time the Transisotor will not be turned on fully, and will thus limit the power going to the motor. Experiment with the values until you have the slope you wish for.
Graylord:
I know, but I'd like to do it through the electronics. My actual goal is to learn electronics
Then I would suggest to follow the advices of electronics experts, instead of coming up with strange ideas and trying to force them thorough whatever it takes.
You could do a simple soft start with a R/C-filter before the transistor/MOSFET.
Any particular reason you are suggestion a lossy RC filter instead of an L(C) filter?
ElCaron:
Any particular reason you are suggestion a lossy RC filter instead of an L(C) filter?
Lossy? OP wants the motor to go slower, but without PWM. Then there is the option of dropping the extra voltage on the transistor for a set amount of time. Yes, energy will be lost, but it's the most simple approach.
Zapro:
Lossy? OP wants the motor to go slower, but without PWM. Then there is the option of dropping the extra voltage on the transistor for a set amount of time. Yes, energy will be lost, but it's the most simple approach.
// Per.
Not always, when it comes to dissipating that energy.
Zapro:
Lossy? OP wants the motor to go slower, but without PWM. Then there is the option of dropping the extra voltage on the transistor for a set amount of time. Yes, energy will be lost, but it's the most simple approach.
// Per.
The resistor will drop voltage and dissipate power all the time during normal operation. How is that a sane idea compared to an LC filter with just as many components? (or less, because the cap is not mandatory)
Then there is the option of dropping the extra voltage on the transistor for a set amount of time. Yes, energy will be lost, but it's the most simple approach.
OP better get good with heatsinks.
There isn't really enough information to give any reasonable answer. What's the stall current of the motor that it needs a soft start? What is the power supply and how much current can it provide? How often is the motor changing state? What's the current of the motor under load?
Switching a LDO regulator to control on/off times of a motor isn't going to work well, and expecting 8V out of a 8V regulator that requires output current won't work either.
If you are trying to learn the electronics end of things, then by all means do so, but it would be wise to do it in a manner that reflects current application and control. There is still plenty to learn, and parts availability won't be so lacking.
Would you go out to your car and rip the ecu, injection system, and ignition system and replace it with points and a carburetor to learn how engines work? Hardly. There was a reason those systems changed.
ElCaron:
The resistor will drop voltage and dissipate power all the time during normal operation. How is that a sane idea compared to an LC filter with just as many components? (or less, because the cap is not mandatory)
For correct operation of a bipolar transistor you NEED the resistor between the microcontroller and the base pin driven.
For a MOSFET, it really doesn't matter unless we talk about high frequency.
The resistor in this case will not waste any more power than it would normally do, sitting before the transistor.
You could do a simple soft start with a R/C-filter before the transistor/MOSFET.
Series resistor from the arduino to a capacitor and then connect that to the base/gate. It will take some time for the capacitor to charge and go to full voltage - in that time the Transisotor will not be turned on fully, and will thus limit the power going to the motor. Experiment with the values until you have the slope you wish for.
// Per.
Thanks, I've found a few examples of doing this with a mosfet, and it seems like the way to go for what I am looking to do.
As for not following other suggestions, I don't mean to offend by avoiding programming, even if it's the simplest way.
I'm already comfortable with programming from my other fields of study. And I am getting into electronics, because, well, I want to learn electronics. So I am purposfully avoiding letting programming do all the work in order to learn various processes and methods behind circuits and components.
I understand that there are better ways to get to the goal, but it's like telling someone why to learn to bake bread, when you can instead learn to use a breadbaking machine. Yes, it's simpler, but my entire purpose is to learn the process itself.