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I am trying to use 4 motors(3-6V 250ma) controlled through 2 L293D Motor drivers. I have a 12V 2A adapter to supply VCC to the motor drivers. I am looking for a way to power my motors without damaging them. I guess using a Voltage regulator(7805) to convert 12v to 5V. I am afraid if 2A will damage my motors. How can I regulate both voltage and current to operate the motors without damaging them? I will be running only one motor at a time.

Muhamed Suhail
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  • 2 amps will likely burn your L293D H bridges. BTW, L293 H bridges are [really bad choices](https://electronics.stackexchange.com/questions/108686/l293-l298-and-sn754410-h-bridge-drivers-on-low-voltage-power-supply). – Andy aka Feb 17 '21 at 12:45
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    the whole L series of chip is prehistoric and probably everything else is better… however he said that he's using small motors (250mA) so even with a 7805 it will not heat up *too much* – Lorenzo Marcantonio Feb 17 '21 at 12:53
  • Will the 2A current burn my motors in any way? How can I use my motors without damaging them? – Muhamed Suhail Feb 17 '21 at 13:07
  • The motors will only draw the current they want. However most motors will draw 3-5 times their rated current at stall, and will burn out if this occurs for very long (> 1 second). Therefore you should ensure that the **mechanical** load does not cause them to draw more than their rated current. If this is not possible then you need a current limiting circuit. – Bruce Abbott Feb 17 '21 at 18:54

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I would recommend to use a buck or step down converter. You can find cheap buck converters on ebay or aliexpress. You need to find a buck converter that works at 12Vin and has a fixed output voltage of 5V (or adjustable). For example, something like shown below would do the job. The advantage of using a buck converter compared to a linear regulator is that it won't get as hot. If you use a linear regulator for the job, you will also need a heatsink that can handle $$Ploss = (12-5)V*2A = 14W$$

A 14W heatsink will be massive. With a buck converter you won't need a heatsink.

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mr_js
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Your idea is correct. You can step down your supply to something amenable (like 5V) and drive your motor with this.

5V or 6V would work but not less since the L293 is only rated from 4.5V and up. Be careful if you use a linear regulator like the 7805 that it will heat up A LOT. Using and heat sink is advised.

As for the current if the motors are not mechanically overload and the voltage is correct they will simply use the current they need. If you are worried fuses were exactly invented for this kind of protection.

Lorenzo Marcantonio
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