electronic genius needed.

[cri_ag]

ok this is not realy car related but it is tech so im not sure if its in the right place.

was working on my mates datto the other day when a dude came up to us and asked if we wanted an electric scooter, he said it just needs a new battery, i said hell yes.

i whipped it apart to find a 12v 20ah sealed lead acid battery, so i swapped in my mates sealed lead acid battery that we going to be running in his datto and gave it a try. no drive, just a click noise from a relay. put the multimeter on the terminals of the motor connection and there is no output coming from speed controler.

so i whipped the cover off the speed controller to find a pcb with two surface mounted relays and four transistors (mosfets maybe?) now my knowledge for diagnosing problems with circuts begins and ends with looking for a component that looks melted and replacing it.

where would the most probable cause of the problem be? the relays click and seem to be supplying power to the part of the circut they need to be, so i dont think its there. and nothing looks toasty so im stumped.



ps. i will get a couple of pics of the pcb up tomorrow if it helps at all.

cheers,
craig.

[Devils]

If the relays click very fast and constantly then i would start with them.

[DeftAnesthetik]

sounds more like a grounding fault/short if anything. disconnect the battery and hook the multimeter to each end of the battery connectors, if you have continuity its grounding somewhere it shouldnt

[river]

Hi,

I doubt a surface mounted relay would have the grunt to run the hi DC amps required to run a scooter motor. So, I'd be looking at the transistors - and if theye are smallish then I'd be thinking they maybe got hot and cooked and don't work no more.

If the circuit is so simple - 2 relays and 4 trannies, then it'd be simple to follow the tracks and darw up the cct diagram. Also check on the net the trannie type (assuming thye are stamped with their number) to get an idea of their characteristics (ie volt/amp/gain, etc) as well as comparable replacement type.

Without knowing more, it is hard to judge what failed.

seeyuzz
river

[driftedmz20]

what river said......

also look for small burn marks on the circuit board or even smell it (sounds werid but i do that alot with pc stuff and you can soon find out what has failed if anything)

[o_man_ra23]

Other one to look for is dry solder joins, look for solder with a matt finish, or legs of components with dark rings around them before the solder.

Simply doing the lead continuity check (obviously with all the switches off) won't find all possible shorts. Also look for fuses... check anything that looks like a fuse.

Check the motor, if it is hard to wind over by hand (should be smooth as river's bottom) then it has likely turned a transistor into a piece of plastic.

[cri_ag]

ok ive checked the relays, they are functioning happily and switching power on. the motor definatly works because i hard wired it onto the battery and went for a test ride!

if the transistors are buggered would i see anything on the outside? or is there a multimeter test i need to do?

when i get home ill whack a few pics up of the pcb.

[river]

Hi,

Need to see the PCB and what type of trannies they are. They hopefully will have a number stamped on them. From there you should be able to see their specs on the net, or maybe in one of my trannie books.

Then, when we know what type of trannies they are, can you check them with a multimeter or other test rig to see if they are okay or blown.

seeyuzz
river

[o_man_ra23]

You have books about trannies?? Dang, that's some fuked up shit right there!!

But I agree with Riverio, there isn't much you can tell by looking at them other than the part number. Once you have test specs, you need to un-solder them individually and run them through the relevant tests.

[Mos]

As an entry level check you can see if the trannies are shorted. None of the pins should have a direct short - if they do, it's blown. It's possible, but unlikely, that there will be a short designed into the circuit outside of the transistor, so this will defn tell you if they are stuffed (unplug as much as you can though).
You can also look for voltage drops across the pins of the trannies (using the diode test) but other circuit components is more likely to affect the results if the tranny is still in circuit.

Easiest way is just to hook up some relays and get really good at doing the on-off thing... Asian mothers with V8 mercs seem to have a good grasp, I'm sure you can learn to ride a scooter like that

Mos.

PS. I still hate wiring.

[river]

Hi,

Fixed for joo!!!!!

PS. I still hate wiring... and upgrading VBulletin... and moving to a new site... and doing IT stuff for Toymods... and... and... and... other stuff too....

nyuk nyuk nyuk

seeyuzz
river

[Mos]

Pretty much anything to do with cars, yes.

[river]

Hi,

You need some old school cars, sunshine. No wires and shit to upset you. Simple analog dashboard, some old dual-throat carbies. Something simple, with a nice suspension and healthy NA engine.... and then have some fun just driving it, rather than working on it.

seeyuzz
river

[o_man_ra23]

That theory goes out the window when the 3S-GTE, power windows, remote central locking, finger print security, electronically opening/closing hatch, and hyperspace bypass button are installed!!

But at least he will look good in his frustrations!!

Hi,

You need some old school cars, sunshine. No wires and shit to upset you. Simple analog dashboard, some old dual-throat carbies. Something simple, with a nice suspension and healthy NA engine.... and then have some fun just driving it, rather than working on it.

seeyuzz
river

[brett_celicacoupe]

checked if there is a fuse or broken wire?

a lot of the time the problem is something simple