Automatic bicycle brake light experience?

[Ykick]

Any experience with something like this?

http://www.personalpitcher.com/store/index.php?main_page=product_info&cPath=76_77&products_id=220

Guessing it's an inertia switch?

 

[docnjoj]

We really need brake lights so my wife doesn't keep running into me when we stop! Seriously! Unfortunately they seem to only let you have these things if you walk into their store. Whaaaaaat! I'm waiting for a call back from them.
otherDoc

 

[Kingfish]

Somebody had one that worked off of Bluetooth/RF wirelessly: The trigger was on the brake lever and sent the signal to the light at the rear. Sort of a “Look Ma, no wires” gimmick.

Search for "wireless brake light". eBay had a few designed for helmets. Here's another for bicycles.

Interesting, KF

 

[ZOMGVTEK]

Is there a brake light output on Infenion controllers?

 

[Kingfish]

Is there a brake light output on Infenion controllers?

Not to my knowledge. The way I did mine was to use a lever-actuated SPDT mini-switch (Radio Shack) for my ebrake, and stack another one right on top for the brake light circuit. See this thread: brake lights posted today.

Lots of ways to skin the kitty.
~KF

 

[icecube57]

Somebody had one that worked off of Bluetooth/RF wirelessly: The trigger was on the brake lever and sent the signal to the light at the rear. Sort of a “Look Ma, no wires” gimmick.

Search for "wireless brake light". eBay had a few designed for helmets. Here's another for bicycles.

Interesting, KF

My local ebike buddy has the maxxon light and it works like a champ.

 

[Ykick]

Thanks for the input folks! Maxxon looks surprisingly good quality...

 

[hillzofvalp]

I think lyen once told me that either EBS- or EBS+ and ground would go high when e brake was applied. Across it I think is full pack voltage, so an appropriate string of LEDs could work. I want to do this sometime.

 

[Kingfish]

I think lyen once told me that either EBS- or EBS+ and ground would go high when e brake was applied. Across it I think is full pack voltage, so an appropriate string of LEDs could work. I want to do this sometime.

EBS- which measures +5VDC, goes to GND when Ebrake is enabled. There's not enough current to run a set of lights. I tried to use it to drive a low-current inline relay: no joy

However, if someone was clever, perhaps use it at the base of a transistor to open a switch... That would be the hat trick :wink:

~KF

 

[docnjoj]

I got two of those original brake lights in the post. Spoke to the owner of the company who didn't think they would sell well. I hope he is wrong. I told hime about ES and he was gunna look us up! They have an inertia switch in them and seem to do what they claim, and are pretty bright too. They come with 3 aaa batts to. I will test them this weekend but they seem to be quite a good idea.
otherDoc

 

[ZOMGVTEK]

I think lyen once told me that either EBS- or EBS+ and ground would go high when e brake was applied. Across it I think is full pack voltage, so an appropriate string of LEDs could work. I want to do this sometime.

EBS- which measures +5VDC, goes to GND when Ebrake is enabled. There's not enough current to run a set of lights. I tried to use it to drive a low-current inline relay: no joy

However, if someone was clever, perhaps use it at the base of a transistor to open a switch... That would be the hat trick :wink:

~KF

Think this can handle 10mA? I have some small SSR's somewhere. I'd assume this +5VDC on EBS- is not isolated from the 5V rail? That would mean you can put the SSR between the +5V and EBS- to make it turn on when EBS- goes low, assuming it can hold a few mA required. Then it would just be a simple matter of running the output to some sort of a regulator. I plan on running my brake light off my 7.5V headlight supply. It would come on dimly when the headlight is on, and go bright when the brake is applied.

I'll try it out sometime over the next few days.

 

[Ykick]

I got two of those original brake lights in the post. Spoke to the owner of the company who didn't think they would sell well. I hope he is wrong. I told hime about ES and he was gunna look us up! They have an inertia switch in them and seem to do what they claim, and are pretty bright too. They come with 3 aaa batts to. I will test them this weekend but they seem to be quite a good idea.
otherDoc

Thanks Doc, 'looking forward to your report. I haven't done anything yet but the idea of an inertia switch seems plausible. I'd like to have a little something to let taxis know when I'm slowing in the heat of battle. Currently, very bad spot getting on the 59th St bridge from 2nd Ave. Horrible, NYC DOT should be keel-hauled for the dangerous mess they've created and left for months.

I seem to remember trailer brake controllers for cars/trucks using inertia switch and in this day and age of cheap, plentiful accelerometers it seems like a viable idea?

Hope that retailer shows up here or at least reads our posts. My biggest problem is/was 'had seen these a month or so ago and forgot the link. When I tried searching, it was very convoluted to find these things. I think some keyword improvement might help product discovery by like-minded folks?

 

[hillzofvalp]

Actually I re read the pm, and he said

EBS+ & GND if you want to trigger the ebrake using the brake light voltage.

So I guess a string of LEDs maybe with a smaller voltage drop in series with the ebike switch will work?

 

[hillzofvalp]

How much power can the 12V bus in the controllers handle? Enough for 10W light? It would be nice to run my light offf the controllers full pack voltage conversion rather than splitting my 20S and putting them out of balance at night.

wow:
http://www.electronicsweekly.com/products/2008/10/03/20431/linear-technology-lt3756-100v-dcdc-converter.htm

http://www.linear.com/product/LT3748

 

[Jeremy Harris]

I think lyen once told me that either EBS- or EBS+ and ground would go high when e brake was applied. Across it I think is full pack voltage, so an appropriate string of LEDs could work. I want to do this sometime.

EBS- which measures +5VDC, goes to GND when Ebrake is enabled. There's not enough current to run a set of lights. I tried to use it to drive a low-current inline relay: no joy

However, if someone was clever, perhaps use it at the base of a transistor to open a switch... That would be the hat trick :wink:

~KF

Here's the circuit for the EBS part of the Xiechang controller:



The EBS- lines go directly to the brake lever switches, which have the other connection connected to ground. If you want to fit low current brake lights than the easy way is to just use the brake lever switches to turn them on directly. If you connect a brake light between a positive supply and the brake lever EBS- connection then the brake light will come on when the lever is pulled, and the controller will still sense the brake application as normal. The diode (D32) is rated at around 50 V I believe, so you're restricted to a low voltage brake light.

 

[Kingfish]

EBS- is from discreet logic and not from the +5 rail and very low current; I should have known this before attempting the relay. Forgive me: I must have been wearing the aluminum-tin hat & witching for a solution with the divining rod again.

The +12VDC rail does not have a lot of capacity and is a bit sensitive. My controller uses the LM317 device (according the schematic), and is typically packaged as TO-220, although I’ve seen it also as a SMD. The specs suggest that the output is 0.5 to 1.5A; enough to drive the FETs and related circuitry, plus supply the +5VDC regulator and logic. It might be tempting fate to tap into it. Actually – truth be known, I am considering using my own +12V supply from a separate DC-DC converter. I just can’t figure out if I can share the isolated GND legs.

D’oh, Jeremy posted as I was composing…
Jeremy, do you mean something like this:

If true, that would be most simplistic as well as awesome
~KF

 

[Jeremy Harris]

Yes, that should work just fine (as long as the LED has some form of current limiting). I reckon you should be OK for half an amp or so through the brake switches, which is probably way more than you need to drive some nice high brightness red LEDs.

 

[hillzofvalp]

Say may 12V source was a Dc dc output from my full pack voltage. What modifications to the above circuit would have to be made for unisolated brake light voltage sources?

 

[Jeremy Harris]

Say may 12V source was a Dc dc output from my full pack voltage. What modifications to the above circuit would have to be made for unisolated brake light voltage sources?

As long as the 12 V source ground is common to the controller ground it'll work fine. The key thing that makes this work is that the controller has a diode internally on the EBS- connection, so it only senses that point being taken to ground. The high side can be pretty much anything up to the diode reverse voltage rating, which I believe is around 50 V.

If you wanted to be ultra safe, or use a higher voltage brake light supply, then you could add an additional diode to the EBS- line with a higher reverse voltage rating. This would need to be a low forward voltage drop Schottky diode, so as to be sure of taking the EBS- pin low enough to trigger.

 

[Kingfish]

Jeremy, I’m hoping for an answer to my DC-DC converter proposal: The supply is 33-75 VDC, and the outputs are +3.3 VDC, and +12 VDC x 2. Grounds on the output are isolated. Presently, I treat both 3.3- and 12-volt circuits as standalone and isolated. At the ebrake, I have two mechanically-activated switches: one for ebrake circuit, and the other for the brake light circuit. Unifying the grounds would allow for me to employ the single-switch solution that you have kindly tendered.

The device application notes for the VKP60MT312 unit do not go into detail about having single grounds, except for uniting the two 12-volt channels for more wattage. Therefore the salient question that I have to you is: Can the device grounds be unified?

Thank you, KF

 

[Jeremy Harris]

Looking at the datasheet for this DC-DC converter it looks as if there will be no problem in tying all the grounds together. As a quick reality check, it might be an idea to stick a meter between the V- output terminals to ensure they really are isolated. If so, there there's no problem in just tying them together.

 

[Kingfish]

Looking at the datasheet for this DC-DC converter it looks as if there will be no problem in tying all the grounds together. As a quick reality check, it might be an idea to stick a meter between the V- output terminals to ensure they really are isolated. If so, there there's no problem in just tying them together.

Gotcha, will do
Many thanks, KF

 

[ZOMGVTEK]

The controllers 12V rail will be perfectly happy with something like a 40mA load?

I'll try and get my brake light wired up this weekend on the 12 FET EB2.

 

[hillzofvalp]

Consider heat sinking the lm317?

 

[Jeremy Harris]

The controllers 12V rail will be perfectly happy with something like a 40mA load?

I'll try and get my brake light wired up this weekend on the 12 FET EB2.

Consider heat sinking the lm317?

Depends on your supply voltage. The controller will typically draw around 50 to 60 mA, and the resistors used to drop the voltage before the LM317 will also be passing this current. These resistors usually run pretty hot on a high voltage controller and adding another 40 mA may well cause them to get just too hot for both them and the LM317 and start causing damage. Adding a heatsink to the LM317 might help, but you also need to deal with the problem of the resistors.

Another problem with doing this for a brake light is that the resistors will drop a different voltage when the brake light comes on than they will with it off. This could potentially cause problems with regulation of the 12 V supply, and if the 12 V supply dips the FETs can blow, from reduced gate drive voltage,

For example, a 48 V controller will usually have around 330 to 380 ohms of total resistance in series with the LM317 (the big power resistors in the lower left region of the board). These will drop around 22 V or so when the controller is operating normally, so the LM317 will have an input voltage of around 26 V on a 48 V supply. This reduces the dissipation in the LM317 and still gives it enough voltage headroom to regulate OK. If you were to draw another 40 mA, then the voltage drop across the resistors would increase to around 38 V. On a 48 V supply the LM317 would then only have an input of about 10 V and as it drops around 3 V when it falls out of regulation this means the 12 V supply will drop to around 7V or so, which is enough to seriously risk FET damage and possibly cause the 5 V regulator to stop working.

All told I don't think its safe to draw any additional current from either the 12 V or 5 V supply on controllers that use dropper resistors before the voltage regulators. The switch mode supply controllers may be OK with a modest additional drain on these supplies, but I don't have one to hand to check.