Tuesday, 5 January 2016

Spectrum/Alpha 4160c LED message board

Im sure you've all seen them, those scrolling LED message displays in shops and offices. Well, I have one, seemingly in working order other than a big chunk knocked off of the end of the case (I have the chunk so thats an easy repair!), acquired from scrap.

But I have a problem. I dont have the correct firmware version to allow me to actually interface to it and make it work! So the hunt is on to find the firmware. The manufacturer wants an extortionate price for an EPROM, so that route is out. At present then im looking at the possibility of reverse engineering it to bypass the built in computer. This would mean a drastic loss of capability, but then just how many ways do you really need an LED sign to scroll, fade, etc?

The EPROM is a 27C1001, which is a 1Mbit (128k x 8) device, so clearly the firmware file for this machine is pretty hefty!

The actual sign is made up of five boards (one of which has the computer piggy-backed to it), each containing the driver capabilities for two rows of five 8x8 bicolour LED matrix units. The driver electronics look to be pretty standard - hex buffer/driver logic, and shift registers.

Heres one of the boards, ive had this one out whilst I metered out the LED matrix pin-outs -

Im not overly impressed I have to say with the power connection in the middle of the board! A proper high current low voltage bus would have been a much better idea!

If I can find a way to get this working, then it will be available for use by the Lions club for any events etc where it would be useful.

Saturday, 2 January 2016

Further on with the Surf PI

Its been quite a while since I worked on the Surf PI metal detector. But, this new year my resolution is to get projects completed!

Before I can work on a proper waterproofed coil, the main electronics need boxing up. It turns out the PCB fits nicely into an ABS case I had bought for another project but not used. This leaves a LOT of free space, enough for the 3x Lithium cells and the loudspeaker. It wont be properly waterproof, but should survive splashes ok.

The battery holder has been secured with impact adhesive, actually a spray on type from Screwfix. The two controls will mount on the top panel, and as can be seen the 4-way avionics type connector for the coil cable is on the bottom panel.

The lid of the box will serve to provide a mounting point onto whatever I decide to use for a shaft.

LiPo battery rebuild - Almost done

After wiring up the low voltage alarm module to the 25-way D female socket, as shown in the last blog entry, Several more steps were needed before finally attaching the LiPo battery pack.

First, the low voltage monitor module required modification. This is because in its original form it was impossible to mount correctly due to the presence of one of the rivets on the casing. Both the alarm LED and the sounders were taken off the PCB and wired onto trailing wires, again a lot of heatshrink was used! Second, an LM35 precision temperature sensor was added, a length of 3 way ribbon cable connecting this to the last three pins of the lower row of the connector.

A 3mm hole for the alarm LED, and a rectangular cut-out for the 7-seg LED display were provided. With the 25-way D type bolted in place, and the LED hot-melt glued in its hole, the main body of the low voltage module could be glued into place. This was a little tricky due to the restricted space to get the glue gun in.

With these sorted, the two alarm sounders were glued to the side wall of the case, using impact adhesive. The photo to the right here shows all the wiring in place, and a layer of foam at the bottom of the case ready to install the battery pack.

Here the battery is finally installed. The main power connectors have been refitted to the case and plugged into the battery, as have the balancing connectors. The temperature sensor is on top of the battery ready to be secured. At this point I tested the output voltage, and using the 'personality' plug, checked that the low voltage alarm module was working.

Now, more foam packing was placed either side of the LiPo pack. The battery is fairly secure now, but I wouldnt trust it as is. A light-weight plywood framework will be created to secure the battery and prevent it moving into the empty space above.

A blob of hot-melt glue and the last task, securing the temperature sensor to the body of the battery, was completed.

 And thats it almost completed. The photo above shows it all in its final configuration, and with the 'personality' plug attached allowing the low voltage monitor to check the battery. I now need to make a charging cable up, complete the framework, and secure the lid. Oh, and add the necessary safety warning labels!

Meanwhile, whilst all the glues were setting, I turned a £1.50 coal shovel into a beach sand scoop for metal detecting, by simply drilling a shit load of 5mm holes into it!

Friday, 1 January 2016

New Year project work

Well, its now next year! 2016 started just 20 minutes ago, so if your mad enough to be reading this and now getting off yer 'ead, happy new year,

Ive a whole stack of things I need to finish off before getting onto any new projects. Unfortunately thats not how it works, and new projects present themselves, as do urgent repair jobs. So, having spent much of new years eve carrying out emergency repairs to fencing, I started by finally getting the speaker sound holes drilled and the speaker mounted to finish off the Chinese airband radio

The only problem is, with the speaker fitted and lid on, the tuning range has gone to pot! Some more adjustment needed I think to the VFO coil. I might introduce an adjustment hole in the lid!

I also got around to trying out the multi-chemistry battery charger, starting with a big 24v NiCd pack for the Clansman radios. This was more an exercise in finding my way around the controls and menus without the risk of doing so with a Lithium pack attached!

Whilst this was running, I progressed some on the LiPo rebuild of the metal cased Clansman battery. The first task was to connect the charger/balancing/activation/protection connector (a 25way D connector) to the LiPo monitor/low voltage alarm.

As you can see, im taking NO chances with this! A short would be catastrophic, so every wire gets heatshrink sleeving. Black for 0v, orange for the HT end, and red for the other cells.

The left hand eight connections of the top row of the connector are wired to the monitor unit. The lower left hand eight are wired to the two balance connectors for the battery. This leaves nine pins spare. Three of these will be wired to an LM35 temperature sensor attached to the battery.

As is, the battery will operate regardless of whether there is anything attached to this socket. But it will not be monitored or protected. A 25way male cable will connect the balancing ports of the battery to the balance ports on the charger, and also the temperature sensor input.

A second male connector acts as a 'personality' plug. Initially, this will simply connect the balance connectors to the monitor module. This will allow me a visual and audible warning of battery level. Should I decide that an active low voltage cut off is needed, this plug will allow me to access the protection circuit to set/reset the trip.

 Next stage then is to cut out a hole for the LED display to be visible, attache the temperature sensor to the battery and the connector, and to fit and mount the battery inside the housing. I also need to make up the balance charger cable.

I also have on my list to repair both my Rogers Ravensbrook tuner/amp, and my Ferranti U1032 valve table set. Ive also a ignition switched 12v - 5v DC-DC converter to install in my car along with cabling to give me a suitable USB power connection for my new dash cam. These will be the main electronic projects for a while.