Backup Detection for Vehicles - Page 1
Forum section: electronics / projects

author: calzap
author_rank: Frequent Contributor
timestamp: November 11, 2015, 05:41:26 am
content: I've been looking for a backup detection system for small/medium tractors. The detection system would be used to activate an audio alarm and perhaps backup lights. There are no backup lights at present, and it's not practical to install a switch inside the transmission. The main gear shift lever (the one that engages reverse) is accessible, but is directly on top of the transmission, and it would be difficult to mount a switch there. In addition, the gear shift levers are between the operator's feet, and any switch or wiring there would take a beating. I've thought of having a photo-electric sensors look for flashing light between holes/slots of the rear wheel hubs, but these are sometimes clogged with dirt, and it wouldn't work in darkness anyway. 12 VDC power is readily accessible.I was thinking of an inertial system or perhaps a radar or sonar sensor pointed at the ground. I've looked on the net without success. Know of any available systems or have ideas how to make one?Mike in California

author: Psi
author_rank: Super Contributor
timestamp: November 11, 2015, 05:46:32 am
content: You could attach a weak and a strong magnet near each other on the drive shaft and detect with a hall sensor.The weak->strong or strong->week would tell you direction.Could also do it with a optical sensor and a saw tooth like protrusion.

author: calzap
author_rank: Frequent Contributor
timestamp: November 11, 2015, 05:48:37 am
content: Quote from: Psi on November 11, 2015, 05:46:32 amDrive shafts are not accessible. It might be possible to do something like this on the wheel hubs.Mike in California

author: Ian.M
author_rank: Super Contributor
timestamp: November 11, 2015, 06:00:37 am
content: Inertial isn't going to work on a rough terrain vehicle. Too much false triggering from jolts etc. Doppler radar or sonar would cost *BIG* bucks. Optical is possible using a mouse sensor with a different long-focus lens, but dirt is going to be a major problem, even with a long shroud on a sensor pointing straight down.The best bet is probably a Bowden cable from near the base of the lever to a spring-loaded switch mounted in a diecast box in a protected location.

author: AndyC_772
author_rank: Super Contributor
timestamp: November 11, 2015, 02:13:51 pm
content: It sounds like you want the system to activate when the driver'sintentis to go backwards, rather than when the vehicle isactuallymoving. If there's something behind it, activating lights and sounds after it's started moving is too late.I don't see any alternative but to detect the position of the gear selection mechanism somehow. Perhaps a magnet and a Hall effect switch?

author: Shock
author_rank: Super Contributor
timestamp: November 11, 2015, 02:32:16 pm
content: http://gardentractortalk.com/forums/topic/11114-diy-reverse-light-74-john-deere-110/The other way is if you have a mechanically driven speedo, you could look for an inline transducer for the speedo cable that only works in one direction (if it exists). But this has a problem as with other motion type solutions, you want the lights to be on before starting to accelerate.http://www.taxicabelectronics.com/images/TransducerAAFord.jpg

author: SeanB
author_rank: Super Contributor
timestamp: November 11, 2015, 06:21:32 pm
content: Bowden cable to the gear lever is probably your best bet, unless you have the room to install an industrial microswitch, which will survive pretty much anything including being used as a foot rest on the body. the switches have various heads which detect mechanical motion, and if you really want contactless you get 3 wire proximity sensors in the same style, or in a small 8mm ( smallest I found cheaply, the M8x1.0 tap cost more to mount it) 2 wire format, that operate from a 12-24VDC system using a series relay load.

author: calzap
author_rank: Frequent Contributor
timestamp: November 11, 2015, 09:30:03 pm
content: Thanks for the responses. The most ideal solution would be a beeper that sounds when the machine is set to go in reverse as opposed to detecting actual reverse movement. However, the latter would be satisfactory. The operator of these machines has excellent rear vision which is why they are not required by U.S. law to have a backup warning signal in the first place. I want to add a beeper as an extra measure of safety. The beeper will not only warn people that the tractor is moving or is about to move backward, but it will discourage operators from leaving the main gear shift in reverse when they get off the tractor. It's fairly common for the operator to put the auxiliary shift lever in neutral, set the parking brake and get off the tractor with it still running. It's not a really dangerous action, but not recommended.There is no speedometer (there is a tachometer, but it would not be of any use). I think it might be possible to use a rod attached to the angled part of the main shift lever and extending forward to a bracket that crosses the steering column. A switch could be mounted on the bracket.See the pic. Top of the pic is toward the front of the tractor and bottom is toward the rear. The two vertical tubes on the right are hydraulic lines. The little box with two wires coming out is part of the neutral detection system. All three shift levers must be in neutral for the tractor to start. The auxiliary shift lever is out of the pic. Markings for gear positions are below the main shift knob. Reverse is down and to the left. Would need to attach a crossbar to the steering column to support a switch, and run a rod from the bend in the main shift lever to the switch. At the crossbar, the rod would have to pivot as well as go back and forth.The switch would have to be able to discriminate between the shift lever being in the R1-2 position versus 2-6 position.Mike in California

author: Rick Law
author_rank: Super Contributor
timestamp: November 12, 2015, 05:12:03 am
content: How about mechanically couple the gear shift-stick to a joystick mounted a few inches away? So the joystick position is a "copy" of the gear shift stick position.Or perhaps two encoders at 12 o'clock and 3 o'clock position, with fixed length rods. The encoders will be turned by some rack and pinion like mechanism to detect the X/Y position of the gear shift stick at a couple of inch above the floor / pivot point.Combining the two encoders you know what gear the transmission is in.

author: Ian.M
author_rank: Super Contributor
timestamp: November 12, 2015, 05:52:06 am
content: As there is no gear up and left, a simple collar clamped round the lever just above the spring retaining clip, holding a short down-curving arm with a magnet on the end, operating an armoured industrial reed switch when the lever is swung to the left, fitted near the base , would be my choice. It would need a bracket secured by the front right and center gearbox cover bolts. Mock it up first to check there is enough magnet movement for reliable operation.

author: calzap
author_rank: Frequent Contributor
timestamp: November 12, 2015, 06:41:28 am
content: Quote from: Ian.M on November 12, 2015, 05:52:06 amThanks Ian. It's pretty much what I've decided to try. I can use a hose clamp around the shaft of the gear shift to secure a flattened L-shaped piece of metal that will extend forward and have a magnet at its end. A magnetic switch can be put on a metal arm attached to the steering column (again with a hose clamp). The forward area is pretty well protected, so a switch there doesn't need to be all that robust. Turned out to be more of a mechanical rather than electronic problem.Mike in California

author: Alexei.Polkhanov
author_rank: Frequent Contributor
timestamp: November 12, 2015, 07:17:53 am
content: I would start from looking at specific model of the tractor. Is there a service manual? Perhaps there is a place for sensor/switch built in already it is just not fitted on your model? I remember doing it on Kubota tractor in 1997 or so - whole "back up" setup with annoying signal and light was sold as a kit for ~$100.

author: calzap
author_rank: Frequent Contributor
timestamp: November 12, 2015, 08:11:35 pm
content: Quote from: Alexei.Polkhanov on November 12, 2015, 07:17:53 amThe tractors are Kubotas, and I have the service and operator's manuals. However, there is no hint of a transmission backup switch or kit for the same. I looked in the protective box over the connections for the neutral position switches, and there are no unused contacts. So, unfortunately, there's no quick solution.Mike in California

author: Kalvin
author_rank: Super Contributor
timestamp: November 12, 2015, 08:33:38 pm
content: Two 3-axis accelerometers. One mounted to chassis and one to the gear shift lever. The relative difference of the angles will tell in which position the level is. Any good?