Schematic for this pwm controller anyone? - Page 1
Forum section: electronics / projects

author: Wimberleytech
author_rank: Super Contributor
timestamp: February 18, 2018, 02:59:42 pm
content: Before, I reverse this, maybe somebody already has a schematic of this controller they would share.Thanks!https://www.ebay.com/itm/12V-40V-10A-PWM-DC-Motor-Speed-Controller-with-Knob-D7Y1-/172622352700

author: amspire
author_rank: Super Contributor
timestamp: February 18, 2018, 03:21:38 pm
content: I don't have the circuit, but it looks like a NE555 (SA555) based circuit with the potentiometer controlling the pulse width of the 555 oscillator. The SA555 is just a lower temperature version of the NE555.The 555 can only run up to 18V, so there is probably a zener on the board to limit the 555 supply voltage.It is a PWM controller for a DC motor. Doesn't set a regulated speed, it just lets you make the motor go faster or slower.

author: Wimberleytech
author_rank: Super Contributor
timestamp: February 18, 2018, 04:45:50 pm
content: Quote from: amspire on February 18, 2018, 03:21:38 pmThanks. I got that much, but there is a jumper on board. Curious about what is there for. I will reverse the thing of nobody produces a schematic.

author: Wimberleytech
author_rank: Super Contributor
timestamp: February 18, 2018, 07:46:24 pm
content: Quote from: Wimberleytech on February 18, 2018, 02:59:42 pmI have traced it out and drawn it in a haphazard schematic, and then did a search for a similar circuit using search term: 555 pwm motor speed controlHappily, I found this schematic which is essentially the core of what I extracted. The only difference is that I found a protection diode in series with the power supply connection and a constant current diode feeding a zener diode, providing the positive supply.But as far as the pwm circuit, I extracted the identical implementation as shown in this schematic.

author: SeanB
author_rank: Super Contributor
timestamp: February 18, 2018, 07:56:58 pm
content: Jumper is a power switch to disconnect the controller and produce no output, using a low current switch so as not to have to switch the full motor current.

author: Wimberleytech
author_rank: Super Contributor
timestamp: February 18, 2018, 08:32:16 pm
content: Quote from: SeanB on February 18, 2018, 07:56:58 pmIndeed.

author: Zero999
author_rank: Super Contributor
timestamp: February 19, 2018, 09:34:13 am
content: Quote from: Wimberleytech on February 18, 2018, 07:46:24 pmWhy not use a MOSFET for Q1? It will have a much lower power loss, than a Darlington pair.The TIP122 is also only rated to 5A continuous, so no good for 10A.47R is probably too low for the base resistor. The maximum base current of the TIP122 isn't specified on the data sheet, but it's certainly less than the >200mA that would flow, when there's a 12V power supply. The NE555's maximum output current rating is also only 200mA, so you're pushing it to the max.https://www.onsemi.com/pub/Collateral/TIP120-D.PDF

author: Wimberleytech
author_rank: Super Contributor
timestamp: February 19, 2018, 01:30:40 pm
content: Quote from: Hero999 on February 19, 2018, 09:34:13 amNo argument here...MOSFET is optimal. But, I am not designing this...I am merely extracting the circuit. I bought one off ebay and wanted to have a schematic. After extracting the 555 portion, I did a google search and found the schematic that I posted with the darlington. I did say that the circuitry was "identical" but, actually, I cannot see the markings on the driver because it is packed between two heat sinks...so I do not know if it is MOS or BJT--so I was incorrect to say "identical."

author: Zero999
author_rank: Super Contributor
timestamp: February 19, 2018, 07:11:32 pm
content: Quote from: Wimberleytech on February 19, 2018, 01:30:40 pmIf you've already got the circuit, then how about replacing the TIP122 with a suitable MOSFET, such as IRFB3806, IRFZ44Z, IRLB8748, IRLB8721, TK30E06N1, NTD4815N-35G? No other modifications are necessary.

author: Wimberleytech
author_rank: Super Contributor
timestamp: February 19, 2018, 07:48:03 pm
content: QuoteImpossible to remove without destroying the board. Thanks for the tip though (pardon the pun).

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 19, 2018, 09:03:50 pm
content: Related thread I put some comments on:https://www.eevblog.com/forum/beginners/ne555-spikes-on-output-why/msg1429612/#msg1429612Actually, the schematic above may well be relevant to that thread...Tim

author: Zero999
author_rank: Super Contributor
timestamp: February 19, 2018, 09:41:45 pm
content: Quote from: Wimberleytech on February 19, 2018, 07:48:03 pmHow is the TIP122 the soldered to the board?Why would removing it destroy the board?

author: Wimberleytech
author_rank: Super Contributor
timestamp: February 19, 2018, 09:58:04 pm
content: QuoteWell, it is mounted on a heat sink which is soldered to the board. Plus, the three legs soldered to the board. I could desolder the transistor easily enough but...it is called a heat sink for a reason...Yes, I could get it off without destroying the board if I had the desire and the patience.At any rate, since I have kicked up so much dust with this simple question, and knowing that everyone is on pins and needles wrt the transistor, I powered it up and took a look at it with a scope--it is a MOSFET.