Broke my throttle!!

[Troy]

Sorry, been away for a few days, I decided to try and remove the sensor from the original throttle and it broke apart, it had been superglued (or something similar) and even careful removal with a scalpal caused it to break. I have now taken the replacement electric scooter throttle apart and apart from slight design differences, it's the same. there are two magnets that move around a tiny hall sensor. All I can assume is that they are different hall sensors that give out different information (remember I'm not an electronics guy, just dabbling), and I guess they don't all work the same. Unfortunately the original sensor has no writing on the bit that I removed as the plastic that covers the sensor split apart and some is still stuck in the throttle. Unless the technician at davinci mobility is able or prepared to tell me the make/model of the original sensor then I'm a bit stuck
It's a bit cheeky to ask bit if anyone has any spare time and is willing to ask the technician (rob I think his name was) at Davinci Mobility (0151 548 1999) what is different about the throttle they supply for the PDQ Powertrike (or what model sensor is inside) I would be very grateful.

 

[flecc]

Bears out what I said previously Troy, it is a perfectly normal throttle and they were trying to say it was something unique to justify the price.

With the machine switched on you should get a DC voltage across two of the three wires coming from the controller to the throttle. If you have multimeter could you measure that DC voltage and let me know what it is?

 

[Troy]

Ok, I've just taken some readings, it's a little dark so if they sound incorrect I'll try again in the morning.

Black wire from multimeter to Black wire from control box
Red wire from multimeter to Red wire from control box, gave me a reading of 2.75volts

Black wire from multimeter to White wire from control box
Red wire from multimeter to Red wire from control box, gave me a reading of 11.68volts

When I accidently touched the multimeter prong against the Black and White wires from the control box the wheelchair nearly ran me over.
When i did the same against the Red and Black wires from the control box there was an audible 'thuddy click' coming from the control box.

I turned the key on the control box which adjusts the setting of the wheelchair from 'full' power to 'half' power and it made no difference to the voltage readings.

I think I've done this correctly, and as you suggested.
A big thank you for all your help so far.
Troy

 

[flecc]

Thanks for those readings Troy. Sorry to ask again, but can you put the two multimeter probes to the black and white wires from the controller and let me know what voltage there is across those? It doesn't matter which way round you use the probes, you'll get a reading either way. Once I've got that reading I can look for possible Hall sensors for it.

Don't put a probe across any two connections shorting them together as you did once there, it can cause damage.

 

[Troy]

Black probe to black cable from control box and Red probe to white cable from control box gives a reading of 'minus' 8.78volts
I was more careful this time, I 'd rather not damage anything else

 

[flecc]

Thanks Troy, I'll investigate the options.

 

[flecc]

Since I don't know the operating current, the gauss of the magnets and other circuit conditions Troy, I can only guess at a likely substitute Hall effect sensor and it is a bit of a long shot. The one I've linked to below may work, and at £2.81 plus VAT ex stock from Farnell you might feel it worth a try. If you scroll down on thepage you'll see a technical data sheet for it, but the head size is 4.5mm x 4.5mm which hopefully will fit into the throttle recess.

Honeywell Hall effect sensor 2SS52M

For the connections, placing the sensor face down with the body chamfers facing you and the leads pointing down, the r/h lead is positive volts, the l/h lead is negative volts and the centre lead is the signal return. I can't give any guarantees, but if your system uses a unipolar sensor, it seems your red lead goes to positive, your white lead to negative and the black lead to the centre signal connection.

If it doesn't work properly the values of the sensor will be most of the problem. If it doesn't work at all, it's possible the system uses a bipolar sensor and that would be impossible to realistically guess at since the variables are too great.

 

[Troy]

I'll order a sensor and give it a go, I will have to cut the stems down a little as it won't fit in the throttle.
Do i have to be careful with the sensor, can it be damaged by static, do I need to wear gloves or ground myself. Is there a maximum wattage soldering iron that should be used?

I really want to say a big thank you for all your help, if it works I'll be very pleased, if not at least I've had a go!
I just wondered if there is anything in the information I gave you that might suggest why the throttle for the electric scooter didn't work (aside of it possibly being faulty)
Troy

 

[Scimitar]

I've just found this page which might be of some help to you...
https://sites.google.com/site/shelbyelectro/Mods-and-technical/general/throttle-repair It doesn't deal directly with yours, but points the way.

 

[Troy]

Hi Dave,
thank you for the link, that's pretty much exactly what I have to do, just hope my soldering skills are up to it!

Flecc
I've just read the spec' of the sensor and it says minimum supply voltage is 3.8v and maximum is 30v. Does that in any way relate to the voltage readings I took from the control box as I was concerned that my lowest reading was 2.75v, obviously this may have no bearing on what I'm doing but I thought I would ask.

one last question, one of the magnets came out of the throttle and I jusy want to check which way it goes back, should they be positioned that if i were to try and put them together they would push apart, or should they snap together!

 

[flecc]

The magnets should snap together Troy, so that they are in effect like one very long magnet with a north and south pole.

Don't worry about the voltages, the magnetic flux determines whether the sensor passes voltage. The voltages you've got are a bit ambiguous and it's still possible that your controller has failed, which may in turn account for the other throttle not working. It's why I think this is worth a try since there's very little expense involved, but beyond this it probably isn't worth experimenting any more if it doesn't work.

 

[Troy]

That's interesting regarding the magnets, as I'd pulled the electric scooter throttle apart I tried to see how the magnets behaved in that ( i marked the magnets 'before' I moved one) and they pushed away from each other, so maybe the throttle is completely different, or is it possible it was assembled incorrectly?

 

[flecc]

They do vary, but one I stripped once and checked the polarity had it's pair acting as one and that seemed to be consistent with the long curved single magnet type I've also seen. It may be that yours is the opposite, I can only suggest to try both ways if one doesn't work as expected.

 

[Troy]

Hi,
I ordered two (one as a back-up) sensors and here's what happened. I connected the wires:
White to the -,
Black to the 0,
Red to the +, (all as suggested). I shrink wrapped the ends so as not to short anything out and did a surprisingl neat job. Placed the sensor back in the throtte in a similar way to how the old one had been positioned, screwed it together and 'Nothing', tried it again with the magnets the other way - Nothing!
Opened it up and just experimented with putting the sensor closer to the magnet and 'hey presto' the front wheel went around. (i raised the front wheel to avoid accidents)
I did my best to move the sensor (by hand) forward and backward between the magnets and what I noticed were two things,
1; as I got close to either magnet it stopped working
2: there was no control over the speed, it just went fast or off
I tried to put the throttle back together but didn't have any success.
As I had a spare sensor I replaced the sensor in the electric scooter thottle and the results are similar except i have managed to put the throttle back together and get some responce, BUT!
It only works when the throttle it turned on approximately half way, full on turns it 'off' and the problem is there is no control over the speed, the wheel skids on a bit of gravel as you try to pull away nomatter how careful you are with the throttle it's just 'on or off!'
I have some thoughts, maybe the sensor isn't the correct one or is there some damage to the control box ( i think this the least likely) or do the wires need to be connected in a different order, if so any idea which one should stay and which two should swap over.
thank you,
Troy

 

[flecc]

This sounds like the problem is the sensor and is either the magnetic flux characteristic being too sensitive to the fitted magnets, or the output current rating unsuitable, or even a combination of both.

The trouble is that as I've said, I'm guessing as to exact type and the variations are mind boggling. Just look at the output current options in the chart in this webpage, and that's without the magnetic flux sensitivity variations which come later in the selection process. I must have come somewhere close for it to have worked at all, but I really am lost as how to refine that without you paying repeatedly for endless variations. Without at least some of the original manufacturer's data it's impossible to know with any certainty where to go from here.

 

[flecc]

Further to the above, if you want to have another go for £1.16, bearing in mind I'm still guessing and it could well fail again, the one I link to below has a halved magnetic gauss sensitivity, switching on and off at roughly 50 gauss instead of 25 gauss as before:

SS461c Hall effect sensor

Connections are with looking at the chamfered rear of the TO92 body with the pins pointing down:

Left pin is + positive, Centre pin is - negative, Right hand pin is output.

 

[Troy]

Hello again, after much deliberation and frustration I chose to purchase a new thottle from davinci mobility, I asked for a discount but was told that the engineer had to work on the throttle to make it suitable and as they charge £45 hour this was why it cost so much (hmm!). It would appear that what this meant was an electrical 3 way 'male' block was attached to the end of the wire so it will plug straight in. This has been done badly and has bare wire exposed where the wire has been stripped. Anyway I digress, but suffice to say it hasn't been done well at all!
I eagerly attached the new throttle and plugged it in - NOTHING! - ARGH!
After walking awaying and calming down I decided to VERY CAREFULLY remove to sensor to find a number on.
UGN 3053u, there is also another couple of number/letters written on the lower line but this is illegible then there looks like a 7 at he end.
I tried the trick of moving a magnet towards the sensor but nothing happens,
I plugged back in my Hall sensor and did the same, I got the wheel going around but as before there was no control over the speed!
At this point I am even more confused than ever, I have looked at the picture I took of the original throttle and compared it with a picture of the new one and it appears that the white cable attaches to one on the outer pins on the old one but the white cable attaches to the centre pin on the new one! 've attached a link to the photographs for you to see for yourself,
Flickr: trojac's Photostream
Any thoughts greatly appreciated
Troy

 

[flecc]

On that UGN3503U, with the branded side uppermost as it's read and the pins towards you, this is the pin-out:

Left hand, Pin 1 = supply positive

Centre, Pin 2 = ground/negative

Right hand, Pin 3 = output

You can check now to see which wire is the positive supply, but since the red lead is to the r/h side, it's probably ok, but worth checking. After that it's just a question of whether the white lead is actually negative/ground, or the black lead as one might expect, with the white lead as output.