Low current electronic speed control for brush DC motor - Page 1
Forum section: electronics / projects

author: paulhdietz
author_rank: Contributor
timestamp: August 22, 2022, 07:59:18 am
content: I have a long running program where we teach kids how to build animatronic shows (think robot theater). I'm working on some new hardware and ran across this board that mostly does what I want. However, I'm using it a bit differently than intended, so I was hoping to find a datasheet for the controller. It is an SO8 marked as an FZ0062090-1. The chip takes a hobby servo control signal, and bidirectionally controls a small brush DC motor up to 1A. But I can't find any info on this chip and I don't recognize the logo. (See link below for pic.) Any help tracking this down would be much appreciated!https://ae01.alicdn.com/kf/A10ee802929604fd5902f90f89464d5dcT.jpg

author: paulhdietz
author_rank: Contributor
timestamp: August 22, 2022, 08:17:15 pm
content: This is another one of these electronic speed controls that uses a different chip, but judging from the logo, probably the same company.Part number on this one is FA030621. See the attached pic.Any help tracking down the manufacturer is much appreciated!--- paul

author: MarkF
author_rank: Super Contributor
timestamp: August 22, 2022, 08:52:26 pm
content: Can't find anything on the chips your referenced.However, I did find thisH-Bridge Motor Controllerfrom SparkFun and a video using an Arduino to drive it:

author: paulhdietz
author_rank: Contributor
timestamp: August 22, 2022, 08:56:30 pm
content: Thanks for the pointer. But the nice thing about the first chip is that it takes a 1-2ms servo control pulse and directly drives a brush motor bidirectionally - no Arduino needed! I'm trying very hard to make all of my stuff accessible to schools with very limited resources, so every penny counts. Thanks!

author: thm_w
author_rank: Super Contributor
timestamp: August 23, 2022, 01:00:26 am
content: Here is a listing, you forgot to link:https://www.aliexpress.com/item/2255800350234860.htmlThere is one SOIC8 on the bottom, one on the top, and a SOT23.SOT23 probably a regulator, one SOIC8 will be the micro, the other will be an H-bridge IC.Similar spec IC with fwd/rev inputs:https://www.holtek.com/documents/10179/116711/HT7K1201v140.pdf1A, 6V

author: paulhdietz
author_rank: Contributor
timestamp: August 23, 2022, 03:28:09 pm
content: Yes, there are many companies selling what appears to be the same module. Thanks for adding a link!Unfortunately, the Holtek part is just an H-bridge. I need to take in a hobby servo style control signal. What I have been doing is using a low end PIC to read the servo command and drive a similar H-bridge (https://lcsc.com/product-detail/Motor-Driver-ICs_Hangzhou-Ruimeng-Tech-MS8838_C1509052.html). But PICs are currently expensive and supply is spotty. The part I'm searching for seems to do most everything I want in one chip. I was hoping someone might recognize the logo to point me in the right direction.Thanks!

author: thm_w
author_rank: Super Contributor
timestamp: August 23, 2022, 10:04:10 pm
content: Quote from: paulhdietz on August 23, 2022, 03:28:09 pmThe board I linked has 2 IC's, one SOIC8 on the top, another on the bottom. So micro and h-bridge.Do you have a board in your possession that is just one IC?Your second image is one IC plus two SOT23's that might be MOSFETs used to drive the motor.

author: james_s
author_rank: Super Contributor
timestamp: August 23, 2022, 10:30:53 pm
content: It may be a chip specifically intended for use in hobby servos. Have you tried just pulling the board out of a cheap servo? You can get those for a few dollars, and if you set the feedback pot in the center, or replace it with a pair of fixed resistors it should behave as you describe.

author: thm_w
author_rank: Super Contributor
timestamp: August 23, 2022, 10:35:45 pm
content: Quote from: james_s on August 23, 2022, 10:30:53 pmGood point, some photos here but couldn't make out the markings:https://newscrewdriver.com/2020/12/29/notes-on-micro-servo-electronics/

author: paulhdietz
author_rank: Contributor
timestamp: August 24, 2022, 01:08:22 am
content: Thanks! That was a helpful link. I don't know how I missed this, but those boards are a two chip solution, so almost certainly a cheap micro and an H-bridge chip, which is what I'm already doing. Mystery solved. I guess I just need to use a cheaper micro than a PIC. Perhaps time to get up to speed with Padauk micros...

author: macboy
author_rank: Super Contributor
timestamp: August 24, 2022, 01:25:11 am
content: Since someone mentioned trying a cheap servo, consider a continuous rotation or 360 degree servo, which has variable rotation speed based on the input, rather than absolute position. The electronics in those then are just simple bidirectional speed controllers. I just don't know if you can get them as cheap as normal servos.

author: james_s
author_rank: Super Contributor
timestamp: August 24, 2022, 01:53:34 am
content: Quote from: macboy on August 24, 2022, 01:25:11 amThey are normal servos, modified exactly as I described, by replacing the feedback pot with a pair of fixed resistors. They also have the stop clipped off the output gear, but that isn't important if you just want the electronics.

author: paulhdietz
author_rank: Contributor
timestamp: August 24, 2022, 01:57:20 am
content: Ironically, what I'm making is an upgraded version of a continuous rotation servo. The key is to use a much higher quality motor with an all metal gear train. These end up with similar speed and torque to the Parallax continuous rotation servos, but in a smaller and more robust form. See the pic. Thanks!

author: james_s
author_rank: Super Contributor
timestamp: August 24, 2022, 02:25:36 am
content: I would just buy some $2-$3 servos and harvest the boards out of them, if you want you can make your own board and just take the ICs. I think you'd be hard pressed to save money over just using the whole board though.