Speed control mobility scooter. - Page 1
Forum section: electronics / repair

author: davelectronic
author_rank: Frequent Contributor
timestamp: August 20, 2021, 12:06:43 pm
content: After recently acquiring a Freerider Mayfair -S mobility scooter, I've been checking off the list tiding it up a bit. It's a 6mph pavement mobility scooter that runs, but with a strange quirk to it. When starting off it's a bit brutal, it's a very sharp and sudden take off from standing still. I've change the throttle potentiometer, suspecting this to be the culprit, but it's definitely not that component. I have looked across the control PCB in the top of the tiller, that all appears ok as well. The speed controller is a sealed unit, so I can't look inside that. Apart from the aggressive take off as you start to move away, it runs fine. The normal start off on other mobility scooters is smooth and linear, and complete travel of the wigwag level is smooth in both forward and reverse. Making use of all travel of the wigwag lever and the potentiometer. I'm at a loss to know why this perticular scooter is aggressive on start off, and level movement equals an abrupt ride.I've adjusted the potentiometer very carefully so it's centred off, and electrical travel is the same as forward and reverse. If I'm gentle with the wigwag lever I can get it to behave smoothly, but if I move a few millimetres of the wigwag lever to far to quickly, and it abruptly takes off. It feels like a very sensitive potentiometer, where start of is very abrupt. So much so whilst adjusting the throttle potentiometer (indoors) it took off suddenly taking out the indoors TV antenna socket on the wall. I have took it a few miles ride to see how it goes, and it's ok, apart from this " touchy" wigwag and potentiometer. Before it was replaced a checked to resistance of the potentiometer with a multimeter, it's fine, smooth and linear travel either side of its centred position. Every thing else functions on the scooter just fine. I can see one preset potentiometer on the control PCB, I have no idea what this does as I can't find a schematic for this control PCB. Thank you for reading, any thoughts or ideas appreciated. I was going to use this as a main daily use scooter, but it's just to touchy on the wigwag lever. I don't want to take out a supermarket shelving unit, or worse and hit another person shopping. Included are the control PCB, and the speed controller images.

author: m3vuv
author_rank: Super Contributor
timestamp: August 21, 2021, 07:27:24 pm
content: firstly is it a brushless 3 phase motor and whats with the bent pins on j8?

author: davelectronic
author_rank: Frequent Contributor
timestamp: August 21, 2021, 07:56:01 pm
content: It's a brushed DC 24 volt motor. The bent pins have been straightened, and I've checked the solder joints. I did check the motor brushes also, and there ok. Once the scooter is on the move it's fine, it just the start off is a bit aggressive, as it does it, your thinking you've put to much input in on start off, so end up stopping. The replacement throttle potentiometer is a like for like replacement, I though it was that causing this problem. But it can not be that potentiometer. I've check the variable speed potentiometer on the control panel, that's ok as well. I just can't understand why it takes off so abruptly, its like the motor isn't seeing the pwm input from the speed controller, or there is a delay in the pwm during start off. The only thing I can think of doing is measure the voltage to the motor during start up, to see if there is a spike as it pulls away. Beyond that I've no idea. The main speed controller unit seems sealed, so can not look into that. The control panel PCB looks fine as well, I have used it a few nights ago, clocking up about 3 miles round trip. Once up to speed it appears absolutely fine.

author: CJay
author_rank: Super Contributor
timestamp: August 22, 2021, 10:33:57 am
content: There's a lot of variance in mobility scooters, from dead basic, nasty things up to highly sophisticated fully programmamble things.Do you know if it's been repaired before and if the speed controller etc. are original parts?What 'reference' voltage is fed to the throttle pot and 'wig-wag' control?Does that reference voltage vary when you move them?What does the output voltage from those pots do?Is the speed controller definitely sealed or is it 'just' glued shut?

author: Manul
author_rank: Super Contributor
timestamp: August 22, 2021, 01:09:01 pm
content: I would say go methodically and confirm that everything from wigwag lever up to speed controller input is working fine.1. Is there one potentiometer for both forward and reverse?2. Are there also some switches? How it senses neutral position? Maybe there is some aligment problem?3. What is voltage on potentiometer?4. Is potentiometer directly wired to speed controller or is there some analog circuitry in between? How the final signal to the speed controller looks? What are voltage levels at forward / reverse / neutral?5. Maybe try to inject external input to speed controller and see how it behaves.If you confirm that all inputs are ok and speed controller is just very sensitive and rough on delivering starting torque, maybe you can add some filtering for analog input in such a way that acceleration is smoothed / delayed, but deacceleration stays fast.

author: davelectronic
author_rank: Frequent Contributor
timestamp: August 22, 2021, 01:33:45 pm
content: Thank you for your replies, you've given me a lot to go on I would or did overlook. Remembering from a previous scooter service, a interface control was connected. I asked what that did, indeed it did alter or change certain input parameters. So it's possible it might need some software values changing. Until I can find means to check if this model of scooter is interfaced with settings, I will start by measuring voltage across complete electrical travel in both forward and reverse. The throttle potentiometer has a stop area on the carbon track at 12 o'clock position, that's 50% electrical travel either side of this break point in the carbon track.These reference voltage values will be a bit more tricky, as I can't find a service manual or schematic anywhere online. But you have definitely given me a lot to look into, some times the obvious is staring you in the face, but you just don't see it. I think it's worth pursuing this for now as the scooter is in nice condition, and once off the line runs along fine. It is just that starting torque is just to much to soon when you gently squeeze the wigwag. I don't know a lot of history of the scooter, it was cheap purchase as rats had destroyed the seat completely. It needed replacing, which wasn't to expensive for a second hand seat. It's looking more positive with all the things I'd completely overlooked.

author: davelectronic
author_rank: Frequent Contributor
timestamp: August 22, 2021, 07:28:54 pm
content: I haven't tried removing it yet, but there is a rubber dome at one end of the control unit. I did try to find out if it's programmable with a device that's often used with changing some parameters. Thinking I might try and get hold of the device that interfaces with the scooter. But.. After seeing the 500 pound price tag for this device, I will give that a miss. Best I've found is 32 pound for a scooter dealer to give it the once over with this piece of hardware. Otherwise I might be looking for a fault the might not exist. Thank you for the help, there's stuff mentioned I would have overlooked had you not said.

author: CJay
author_rank: Super Contributor
timestamp: August 22, 2021, 08:27:01 pm
content: Quote from: davelectronic on August 22, 2021, 01:33:45 pmYeah, if rats have been at it I'd definitely be looking at the wiring as rat urine is nasty stuff, they tend to enjoy chomping on wiring too.Ref voltages aren't necessarily as much of a problem as you might think, what you need to see is if they change abruptly or if there's something vaguley sensible

author: Manul
author_rank: Super Contributor
timestamp: August 22, 2021, 08:47:53 pm
content: Does it also start rough in reverse? Anyway, I would definetly give it a go and at least observe signals going to the speed controller. It might be something simple.I'm interested how neutral position works. There should be some dead zone between forward and reverse to account for slight mechanical misalignment. If there is just one potentiometer, no switches, nothing else, then there should be some "window" in the middle of that pot signal measured as dead zone. Maybe control board and speed controller senses that zone differently and when control board enables speed controller it abruptly starts. Just speculation.

author: Ian.M
author_rank: Super Contributor
timestamp: August 22, 2021, 08:56:28 pm
content: First you need to be certain that the previous owner wasn't in any way connected to Colin Furze, or Photonicinduction . . . .More seriously, rough starting could be due to a mechanical problem, e.g. excessive stiction. Check the bearings!

author: Manul
author_rank: Super Contributor
timestamp: August 22, 2021, 09:08:10 pm
content: Looks same / similar. Might be useful.

author: amyk
author_rank: Super Contributor
timestamp: August 23, 2021, 02:52:07 am
content: Does it still start as abruptly with the wheels raised off the ground?Does the motor have speed feedback (tacho)? Maybe it's putting out a weak signal at low speeds.

author: davelectronic
author_rank: Frequent Contributor
timestamp: August 23, 2021, 12:51:43 pm
content: There's a few more things in your replies I've yet to check. Hadn't realised until you mentioned these things. Rats made the seat fall apart when my Son removed it, I though it was just a sloppy seat mechanism that needed tightening. I doubt I'd have bought it if I had seen underneath the seat. Rats had torn through the seat vynal and into the wood construction. I will check the wiring again. No I haven't tried with the wheels off the floor yet, but it's definitely worth jacking up the back just to see what it's like with no load.I'm going to try seeing if that rubber dome is removable, if there is a 4 pin molex connector under there, I'm going to see if I can arrange to just check the control parameters are good at one of the local mobility stores. Hopefully that's the problem, and a software tweak fixes it. And I've still got the old throttle potentiometer, out of interest I will prize it open to see the carbon track. I'd have a Colin Furze scooter over the 8mph main scooter i have at the moment, great fun. I'd missed Photonicinduction, he was away for a few years, but he's back now. Love both there crazy stunts and mind blowing projects. So far on this mobility scooter I've replaced the tyres, replaced the seat, and installed a new throttle potentiometer. The scooter runs fine once it's on the move, it's just that start up, I wouldn't won't to take out a supermarket shelving unit with it. At the moment it's going to be a back up scooter, as the elevator breaks down on a weekly basis. So outside in a lock up garage is the go to scooter when the elevator is down. As I can get the road scooter out if the elevator is broken down. I'm lucky I've got my Son for help, he starts college soon to train to be a mechanic. The scooter is tidy, so worth trying to get it running right. The best thing is the batteries seem to have had very little use, that saves a lot, as those batteries are really expensive.

author: davelectronic
author_rank: Frequent Contributor
timestamp: August 23, 2021, 07:48:36 pm
content: There is indeed a socket on the control unit, under the rubber dome shaped cover. It has 5 pins and an index slot in it, looks like mini din to me. But nowhere on the web can I find the cable or device that interfaces that socket. Looks like I will contact the local store, see if they can check the current parameters, and adjust any that might need that. Don't understand why there's no results from searching this programming device. I found the molex type programming device, but not one with a mini din plug.

author: geggi1
author_rank: Frequent Contributor
timestamp: August 23, 2021, 10:14:59 pm
content: If there is some kind of break controlled by the throttle there might be a fault on when the break will release.In case there si something wrong with the break release the softstart might be ok, but the break will release to late. The scooter will accelerate a until the level set by the throttle.If you got an oscilloscope you can check the timing between the break and energizing of the motor.

author: davelectronic
author_rank: Frequent Contributor
timestamp: August 24, 2021, 12:10:47 pm
content: It had crossed my mind, as it's that latching of the break when stopping, and it's like squeeze the lever for forward and thinking come on, when's it going to realease and move. Then keep squeezing for forward, and suddenly abruptly it moves kind of shooting forward abruptly, it's the same in reverse. It does feel like it's not realeasing early enough. But it could be adjusted in software (maybe) or it could well be a break fault. I did clean off a lot of aluminium corotion, but as the break functioned, I didn't think it could be that. The scooter was a bargain at £200 It's looking less of a bargain now. Second hand replacement seat, new set of tyres, new throttle potentiometer, and perhaps a service and possibly more parts..PS. I do have an old Hameg ocilliscope 60mhz but it's not a storage scope.

author: Manul
author_rank: Super Contributor
timestamp: August 24, 2021, 01:16:37 pm
content: Maybe you can disable / disconnect brakes for test purposes and try how it behaves (somewhere safely).

author: Ian.M
author_rank: Super Contributor
timestamp: August 24, 2021, 01:41:16 pm
content: With some series resistors or potential dividers, and 4.7V Zeners to clamp the signals (as I'm betting they are up to 24V with inductive spikes on top), you can use a dirt-cheap Salae Logic 8 clone USB logic analyser with the FOSSSigrok Pulseviewsoftware to check signal timing for up to eight signals. If you've got Amazon prime, you could have one through your letterbox by the end of tomorrow for only £6.You'd still need to use your Hameg scope to check the signals the logic analyser is digitizing are the shape you expect,but once you are reasonably confident of that, you can log their on/off state for quite long intervals, maybe to a laptop in the basket while (cautiously) driving around.

author: davelectronic
author_rank: Frequent Contributor
timestamp: August 25, 2021, 12:46:38 pm
content: If I disable the break I'm not totally sure, but it might not move at all. This is seen as a fault problem and the scooter might not move at all. But yes I can try and see what happens if I disconnected it. Mostly my knowledge is analogue electronics, and even then I'm a modest hobbyist. The software approach is probably beyond my ability level. I only have desk top PC, no laptop unfortunately. It looks like an interesting option to try, but I don't know if it's beyond my skill level. Thank you for the wiring diagram above, that is definitely the circuit. I can see the din socket at the far left looking at the control unit at the front.

author: CJay
author_rank: Super Contributor
timestamp: August 25, 2021, 06:00:27 pm
content: Post up a pic of the back of the board the 'wig wag' connects to?Also, can you confirm the bent TO-92 device isn't shorting out or has broken leads?

author: davelectronic
author_rank: Frequent Contributor
timestamp: August 26, 2021, 02:11:31 pm
content: I did give the solder side of the pcb a good look under a large light magnifier. I couldn't see any bad joints, or dry one's, it's a single sided PCB through hole circuit.

author: geggi1
author_rank: Frequent Contributor
timestamp: August 26, 2021, 03:53:22 pm
content: Look for dry solders and components that looks fried.The PCB don look that large so it might be an idea to just refresh all the solder pads.

author: Manul
author_rank: Super Contributor
timestamp: August 26, 2021, 05:00:41 pm
content: I feel that we will move nowhere until we actually start measuring things and talk electronics.

author: davelectronic
author_rank: Frequent Contributor
timestamp: August 26, 2021, 06:55:15 pm
content: Yes, I will pull out the multimeter another day and start measuring from power in, following until, or if something doesn't seem right. I'm still pinning some hopes on it being a software parameter issue. The only thing is I can not see a dealer or service engineer letting it leave to store or workshop with such abrupt control parameters. I'm not ready to give up yet.

author: m3vuv
author_rank: Super Contributor
timestamp: August 26, 2021, 08:28:37 pm
content: i cant see bad solder joints causing this,i imagine if that was the case it would be just an intermitent non start.

author: CJay
author_rank: Super Contributor
timestamp: August 27, 2021, 07:55:37 am
content: Quote from: davelectronic on August 26, 2021, 02:11:31 pmI dunno which board that is but it's not the one in the first post.

author: davelectronic
author_rank: Frequent Contributor
timestamp: August 27, 2021, 01:01:51 pm
content: Yes it's the same board, not a very good image as taken in poor light and flash not working. I have two of some components (pcb's) I'm sure I've got the right one photographed. I will double check. I've acquired a few spare parts from a friend that has scrapped a bit of electrical stuff, I asked him if he comes across control units and any tiller circuit boards if he'd keep them for me. Probably never need them, but they don't take up much space. All I know is the solder side of the tiller circuit board looks fine. I think the software parameters need looking at first. Then if there ok, then there is a fault somewhere.

author: aqibi2000
author_rank: Regular Contributor
timestamp: August 28, 2021, 08:13:53 am
content: What do you understand from circuit boards?There are basically no high power semiconductors shown anywhere on your pcb and ONLY relays.Only 1 high wattage ceramic resistor at the bottom which I believe would be the soft start… check this and it’s subordinatesTherefore it’s not variable speed it’s all relay driven, as simple as can be!

author: davelectronic
author_rank: Frequent Contributor
timestamp: August 28, 2021, 01:19:33 pm
content: The control unit is responsible for the pwm to the motor. That's rated at 24 Volts 70 Amps, I understand the tiller PCB circuit is mostly low power relays, one or two would be responsible for switching a larger contactor in the motor controller. My knowledge is that of a hobbyist that is interested in analogue electronics. I can get the scooter to crawl along slowly, but for slowly to full speed is to sudden, with not much variable control Inbetween very slow to full speed. So it doesn't behave very linear across the electrical travel of the throttle potentiometer. I'm going to have a look at the software parameters first I think, as if I change any components, it could inevitably affect these parameters where it's not intended. If that doesn't fix this, I might replace the motor controller and electrical brake. It can not be direct relay start at full power, just relay on or off. Have you ever applied full voltage to a brushed DC motor and noted the sudden huge torque that creates. If it where like that, it would very quickly destroy the motors armeture and commutator, and probably the start relay. It has to be low voltage controlling the motor controller, implicating pwm as the control mode.

author: aqibi2000
author_rank: Regular Contributor
timestamp: October 01, 2021, 09:41:16 pm
content: Replace it with your own BTS7960 43a brushed controller.Easy to control, use and interface to. And only £7

author: CJay
author_rank: Super Contributor
timestamp: October 01, 2021, 09:49:40 pm
content: Quote from: aqibi2000 on October 01, 2021, 09:41:16 pmWhich will fry in seconds if you try and use it for the motor in that scooter.

author: DavidAlfa
author_rank: Super Contributor
timestamp: October 02, 2021, 04:09:31 am
content: Check the blue module, that's what makes the power regulation.Also, it could be a mechanical problem, like backlash in the gears.