Driving a linear voice coil actuator with an audio amplifier - Page 1
Forum section: electronics / projects

author: streamline
author_rank: Newbie
timestamp: February 19, 2024, 05:21:03 pm
content: Hello,Coming from the simulator racing hobby I have recently put bass-shakers/transducers (Dayton BST-1) onto the chassis of my simulator to reproduce suspension and road-effects that happen in the game by making the seat and foot-rest rumble. I have seen people doing similar things with their pedals to, for instance, reproduce an ABS effect if they are braking too hard in the simulator.However, since transducers, especially the smaller ones that people mount to their pedals, are meant to reproduce effects in the 50-150hz range, I have thought that instead of using small transducers for the pedals, it might be interesting to use linear voice coil actuators instead. I got the idea from a products called the P-HPR by the brand Simagic. From the looks they seem to be LVCAs attached to a specialized controller. They are able to reproduce effects in the 1-20hz range with a lot of power and can much better simulate the effect of how ABS would feel in a real car.Now this is where my complete lack of knowledge in the electronics field will become very apparent and why I have come to this forum to get some advice and/or opinions on my idea. I am but a humble backend developer by trade.Since, from what I can see, voice-coil actuators from a hardware standpoint are the same as what is used in speakers, like the bass-shakers that I am using on my chassis.I did do some research and could not find anyone attempting this before. I also found that there are specialized drivers (like the Texas Instruments DRV2605) to use in combination with LVCAs. Some even have pre-saved effect libraries or can work with audio signals / waveforms. However, I have no idea how I would put together a project and build my own amplifier with this chip, so my idea was to take a shortcut and just use an audio-amplifier with for instance a Texas Instruments TPA3116D2 instead.So my question is, is it possible to use a LVCA and pair it up with a audio amplifier? Or is this specialized controller used by the above mentioned product necessary to achieve what I am after?

author: CaptDon
author_rank: Super Contributor
timestamp: February 19, 2024, 06:23:06 pm
content: Many audio amplifiers fall off like a rock below 20Hz. You need probably a Class-D switched mode amplifier that has flat response down to about 5Hz and you probably need a lot of power like 500 watts RMS or maybe more. Look at some of the so called 'Plate' subwoofer amplifiers. Many of them can drive as low as 2 ohms. Not sure what the impedance of your actuator may be?? You could probably just feed the input signal directly to the amplifier. Beware of the bogus D.J. bullshit amplifiers promising 4 kilowatts of output with only a 5, 8 or 10 amp line fuse!!! How do you get 4 KW from 120 volts on a 15 amp outlet anyway??? You can store energy in capacitors for 'peaks' but you sure as hell can't hold a steady 4 KW tone on a 120 volt 15 amp receptacle, although the garbage amplifier specs make you think you can. Some of those multi-kilowatt amplifiers can barely manage 250 watts RMS steady tone without clipping, distorting or just burning up!!

author: themadhippy
author_rank: Super Contributor
timestamp: February 19, 2024, 06:57:28 pm
content: Quotesame way lab gruppen get 10kw at 32A with 110v,or 16A in 240v land

author: David Hess
author_rank: Super Contributor
timestamp: February 19, 2024, 08:29:00 pm
content: Audio amplifiers usually include a high pass filter somewhere around 20 Hz to keep rumble out of the speakers. Otherwise they will work fine.I would look for a class-D subwoofer amplifier and if necessary modify it to lower the low frequency cutoff.

author: Smokey
author_rank: Super Contributor
timestamp: February 19, 2024, 09:38:13 pm
content: Speakers typically are voice coils. Essentially the same mechanism.Get an amp that is not AC coupled, and make sure the input signal is zero referenced and symmetrical and you should be able to go as low frequency as you want. You can put out DC if you wanted (High bandwidth voltage controlled voltage source anyone?)...Good to go!

author: Benta
author_rank: Super Contributor
timestamp: February 19, 2024, 10:27:16 pm
content: I'd say you need quite a lot of power output to get real ABS feeling (or other sensory feedback).A start might be the famous LM3886 power amp from TI.No problem DC coupling that one, so that's one hurdle passed.The question is, whether 60 W is enough.

author: SiliconWizard
author_rank: Super Contributor
timestamp: February 19, 2024, 10:32:26 pm
content: I think I would use a DC motor for this instead.

author: shakalnokturn
author_rank: Super Contributor
timestamp: February 20, 2024, 12:53:36 am
content: Quote from: SiliconWizard on February 19, 2024, 10:32:26 pmSame here: DC motor, reduction gear, small displacement crankshaft style mechanism, spring, pedal arm.Just a DC motor with sufficient flyweight a larger version of those used for rumble in game controllers directly attached to the pedal arm could be enough to give the ABS feel. Frequency can be controlled to some extent too.

author: streamline
author_rank: Newbie
timestamp: February 20, 2024, 06:48:09 am
content: Quote from: SiliconWizard on February 19, 2024, 10:32:26 pmPeople are doing this but since the P-HPR product by Simagic has come out, they are saying that there is no comparison. The issue with rumble-motors is that they take a while to spool up and can't give immediate response and also the frequency would be too high. The great thing about the linear actuator is that it can give immediate hits at full strength. The next best thing are transducers mounted to the pedal, but again the issue here is the frequency. It gives feedback, but it's not realistic.Quote from: Benta on February 19, 2024, 10:27:16 pmThe parameter section of the product page of the motor states a 11.5V operating voltage with a 24ohm resistance and 0.6A current rating for a max. thrust of 400 grams. So that's 7.2 watts? I just found the parameter page now, maybe I should have gone for another model with more thrust. But I think it's more about momentum and operating speed than total thrust here. Either way, for a proof of concept it's enough.

author: streamline
author_rank: Newbie
timestamp: March 18, 2024, 02:23:47 pm
content: Got the motor today and it works:https://www.youtube.com/shorts/n9--i0m_814Feedback is pretty decent at 12V and 24VI'll design a housing for it and 3D print it