I'm looking for a power amplifier that can drive water pumps (this system) at variable speeds in order to control water levels in tanks. This is for an engineering teaching lab. The amp should output up to 24 V at 100 W, with a voltage gain of 3 (relative to the input voltage). The supplier is recommending a power amp but I'm looking for off-the-shelf alternatives to that amp. As I look around online, I'm having trouble finding something that isn't an audio amplifier. What is the name for what I'm looking for? What should I Google?


closed as off-topic by Jasen, Transistor, Elliot Alderson, Blup1980, RoyC Jan 12 at 15:57

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    \$\begingroup\$ You are short of specifications. Please edit your question to explain if you are looking for variable speed control (what range) or constant speed control. What is the "voltage gain of 3" about? What is generating the control voltage? Why would a lab bench power supply not suffice? \$\endgroup\$ – Transistor Jan 11 at 23:17
  • \$\begingroup\$ What voltage output range do you need? You say you need 24V, is this 0 to 24V? or just straight 24V? \$\endgroup\$ – laptop2d Jan 11 at 23:24
  • \$\begingroup\$ you want to buy or build? \$\endgroup\$ – Jasen Jan 11 at 23:49
  • \$\begingroup\$ @Jasen I want to buy something. \$\endgroup\$ – Alex Szatmary Jan 11 at 23:58
  • \$\begingroup\$ unfortunately shopping questions are off-topic. \$\endgroup\$ – Jasen Jan 12 at 0:07

You actually need +/24V @ 4A if that was suggested. But it all depends on your acceleration and speed demand. 50W gives 1/2 torque and RPM.

To do this, depending on your pump acceleration, you may need a reserve capacity > 100W or not. Typically motors use 5 to 10x rated current on full voltage start. So a ramp start is better.

The best solution for power is a 24V battery with a trickle charger because of the cranking current capacity or low ESR with a cheap 20A PWM motor speed controller with gain.

The cheapest solution is a universal 24V 4A laptop charger. https://www.banggood.com/AC-100V-240V-DC-24V-4A-96W-Power-Supply-Charger-Converter-Adapter-p-970663.html?rmmds=search&cur_warehouse=CN with a PWM motor speed control board rated for 5x the current like 10 or 20A. for $10 with fan when needed.

Otherwise Audio amps are usually stereo so 100W is actually 50+50 and you would need a 200W stereo or 100W mono unless you had 2 such systems to control. The cheapest cost here is $0.15/W from Banggood in 50+50W systems. That means your pump only goes half max speed if rated for 24V but still works.

100W cheap https://www.banggood.com/AC-100V-240V-DC-24V-4A-96W-Power-Supply-Charger-Converter-Adapter-p-970663.html?rmmds=search&cur_warehouse=CN but not as reliable so get 2.

20A driver $50 https://www.ebay.com/i/123582962532?chn=ps&dispItem=1

If you wanted digital control, there are many with USB interface. This one is more than you need https://www.robotshop.com/ca/en/sabertooth-dual-2x32a-6v-24v-regenerative-motor-driver.html?gclid=Cj0KCQiAmuHhBRD0ARIsAFWyPwj8goYFI9DrjU_M9EIaslp7uu4dwMlnrOQVLryy0MSJgf4Ef8NBaWMaAoelEALw_wcB

Cheapest 43Apk 28V motor driver https://www.banggood.com/Semiconductor-BTS7960B-43A-HBridge-Motor-Driver-Module-For-Arduino-p-928634.html?rmmds=search&cur_warehouse=CN


that amplifier is overkill, seeing as it's a pump and you only need to run it in one direction, you could take a 5A buck converter and modify the feedback path by addign an op-amp and some gain control.

That, a 36V 3A power supply, and a case would get you there for about $40 in parts


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